MOSCOW (AP) — A long-feared Russian invasion of Ukraine appeared to be imminent Monday, if not already underway, with Russian President Vladimir Putin ordering forces into separatist regions of eastern Ukraine.

A vaguely worded decree signed by Putin did not say if troops were on the move, and it cast the order as an effort to "maintain peace." But it appeared to dash the slim remaining hopes of averting a major conflict in Europe that could cause massive casualties, energy shortages on the continent and economic chaos around the globe.

Putin's directive came hours after he recognized the separatist areas in a rambling, fact-bending discourse on European history. The move paved the way to provide them military support, antagonizing Western leaders who regard such a move as a breach of world order, and set off a frenzied scramble by the U.S. and others to respond.

Underscoring the urgency, the U.N. Security Council set a rare nighttime emergency meeting on Monday at the request of Ukraine, the U.S. and other countries. Ukraine's president, Volodymyr Zelenskyy, sought to project calm, telling the country: "We are not afraid of anyone or anything. We don't owe anyone anything. And we won't give anything to anyone."

The White House issued an executive order to prohibit U.S. investment and trade in the separatist regions, and additional measures — likely sanctions — were to be announced Tuesday. Those sanctions are independent of what Washington has prepared in the event of a Russian invasion, according to a senior administration official who briefed reporters on the condition of anonymity.

The developments came amid a spike in skirmishes in the eastern regions that Western powers believe Russia could use as a pretext for an attack on the western-looking democracy that has defied Moscow's attempts to pull it back into its orbit.

Putin justified his decision in a far-reaching, pre-recorded speech blaming NATO for the current crisis and calling the U.S.-led alliance an existential threat to Russia. Sweeping through more than a century of history, he painted today's Ukraine as a modern construct that is inextricably linked to Russia. He charged that Ukraine had inherited Russia's historic lands and after the Soviet collapse was used by the West to contain Russia.

"I consider it necessary to take a long-overdue decision: To immediately recognize the independence and sovereignty of Donetsk People's Republic and Luhansk People's Republic," Putin said. 

Afterward he signed decrees recognizing the Donetsk and Luhansk regions' independence, eight years after fighting erupted between Russia-backed separatists and Ukrainian forces, and called on lawmakers to approve measures paving the way for military support. 

Until now, Ukraine and the West have accused Russia of supporting the separatists, but Moscow has denied that, saying that Russians who fought there were volunteers.

At an earlier meeting of Putin's Security Council, a stream of top officials argued for recognizing the regions' independence. At one point, one slipped up and said he favored including them as part of Russian territory — but Putin quickly corrected him.

Recognizing the separatist regions' independence is likely to be popular in Russia, where many share Putin's worldview. Russian state media released images of people in Donetsk launching fireworks, waving large Russian flags and playing Russia's national anthem.

Ukrainians in Kyiv, meanwhile, bristled at the move. 

"Why should Russia recognize (the rebel-held regions)? If neighbors come to you and say, 'This room will be ours,' would you care about their opinion or not? It's your flat, and it will be always your flat," said Maria Levchyshchyna, a 48-year-old painter in the Ukrainian capital. "Let them recognize whatever they want. But in my view, it can also provoke a war, because normal people will fight for their country."

With an estimated 150,000 Russian troops massed on three sides of Ukraine, the U.S. has warned that Moscow has already decided to invade. Still, Biden and Putin tentatively agreed to a meeting brokered by French President Emmanuel Macron in a last-ditch effort to avoid war.

If Russia moves in, the meeting will be off, but the prospect of a face-to-face summit resuscitated hopes in diplomacy to prevent a conflict that could cause massive casualties and huge economic damage across Europe, which is heavily dependent on Russian energy.

Russia says it wants Western guarantees that NATO won't allow Ukraine and other former Soviet countries to join as members — and Putin said Monday that a simple moratorium on Ukraine's accession wouldn't be enough. Moscow has also demanded the alliance halt weapons deployments to Ukraine and roll back its forces from Eastern Europe — demands flatly rejected by the West.

Macron's office said both leaders had "accepted the principle of such a summit," to be followed by a broader meeting that would include other "relevant stakeholders to discuss security and strategic stability in Europe."

U.S. national security adviser Jake Sullivan, meanwhile, said the administration has always been ready to talk to avert a war — but was also prepared to respond to any attack.

Putin's announcement shattered a 2015 peace deal signed in Minsk requiring Ukrainian authorities to offer broad self-rule to the rebel regions, a major diplomatic coup for Moscow.

That deal was resented by many in Ukraine who saw it as a capitulation, a blow to the country's integrity and a betrayal of national interests. Putin and other officials argued Monday that Ukrainian authorities have shown no appetite for implementing it.

Over 14,000 people have been killed since conflict erupted in the eastern industrial heartland of in 2014, shortly after Moscow annexed Ukraine's Crimean Peninsula.

Potential flashpoints multiplied. Sustained shelling continued Monday along the tense line of contact separating the opposing forces. Unusually, Russia said it had fended off an "incursion" from Ukraine — which Ukrainian officials denied. And Russia decided to prolong military drills in Belarus, which could offer a staging ground for an attack on the Ukrainian capital, Kyiv.

Ukraine and the separatist rebels have traded blame for massive cease-fire violations with hundreds of explosions recorded daily.

While separatists have charged that Ukrainian forces were firing on residential areas, Associated Press journalists reporting from several towns and villages in Ukrainian-held territory along the line of contact have not witnessed any notable escalation from the Ukrainian side and have documented signs of intensified shelling by the separatists that destroyed homes and ripped up roads. 

Some residents of the main rebel-held city of Donetsk described sporadic shelling by Ukrainian forces, but they added that it wasn't on the same scale as earlier in the conflict.

The separatist authorities said Monday that at least four civilians were killed by Ukrainian shelling over the past 24 hours, and several others were wounded. Ukraine's military said two Ukrainian soldiers were killed over the weekend, and another serviceman was wounded Monday.

Ukrainian military spokesman Pavlo Kovalchyuk insisted that Ukrainian forces weren't returning fire.

In the village of Novognativka on the Ukraine government-controlled side, 60-year-old Ekaterina Evseeva, said the shelling was worse than at the height of fighting early in the conflict.

"We are on the edge of nervous breakdowns," she said, her voice trembling. "And there is nowhere to run." 

In another worrying sign, the Russian military said it killed five suspected "saboteurs" who crossed from Ukraine into Russia's Rostov region and also destroyed two armored vehicles and took a Ukrainian serviceman prisoner. Ukrainian Border Guard spokesman Andriy Demchenko dismissed the claim as "disinformation." 

Amid the heightened invasion fears, the U.S. administration sent a letter to the United Nations human rights chief claiming that Moscow has compiled a list of Ukrainians to be killed or sent to detention camps after the invasion. The letter, first reported by the New York Times, was obtained by the AP. 

Kremlin spokesman Dmitry Peskov said the claim was a lie and no such list exists.

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Karmanau reported from Kyiv, Ukraine, and Cook from Brussels. Lori Hinnant in Kyiv; Angela Charlton in Paris; Zeke Miller and Aamer Madhani in Munich, Germany; Geir Moulson in Berlin; and Eric Tucker, Ellen Knickmeyer, Robert Burns, Matthew Lee and Darlene Superville in Washington contributed to this report.

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THIS WAS AN EARLIER STORY MONDAY:

WARSAW, Poland (AP) — World leaders are making another diplomatic push in hopes of preventing a Russian invasion of Ukraine despite growing tensions even as the Kremlin considers recognizing the independence of the two separatist regions in eastern Ukraine and shelling continues in those areas.

The White House said President Joe Biden had agreed “in principle” to meeting with Russian President Vladimir Putin if he refrains from launching an assault on his neighbor that U.S. officials say appears increasingly likely.

A Biden-Putin meeting would offer some new hope of averting a Russian invasion that U.S. officials said could begin any moment from the estimated 150,000 Russian troops that have amassed near Ukraine.

Here is a look at the latest developments in the security crisis in Eastern Europe:

PUTIN MULLS INDEPENDENCE FOR SEPARATIST REGIONS

Putin convened top officials Monday to consider recognizing the independence of the Russia-backed separatist regions in eastern Ukraine.

A U.S. official said that a recognition of the two regions would be “condemnable.”

“If carried out, this would again result in the upending of the rules-based international order, under the threat of force,” Michael Carpenter, the U.S. ambassador to the OSCE, told a special session of the organization in Vienna.

The meeting of Putin’s presidential Security Council follows televised statements by separatist leaders, who pleaded with Putin to recognize them as independent states and sign friendship treaties envisaging military aid to protect them from what they described as the ongoing Ukrainian military offensive. Russia’s lower house made the same plea last week.

Ukrainian authorities deny launching an offensive and accuse Russia of provocation amid intensifying shelling along the line of contact.

WILL BIDEN AND PUTIN MEET?

The U.S. and Russian presidents have tentatively agreed to meet in a last-ditch diplomatic effort to stave off Moscow’s invasion of Ukraine.

Yet but both seem cautious about a possible meeting.

The White House says the meeting will only happen if Russia does not invade Ukraine, noting that heavy shelling is continuing in eastern Ukraine.

Kremlin spokesman Dmitry Peskov, for his part, said Monday that “it’s premature to talk about specific plans for a summit.”

French President Emmanuel Macron sought to broker the possible meeting between Biden and Putin in a series of phone calls that dragged deep into the night. Macron’s office said both leaders had “accepted the principle of such a summit,” to be followed by a broader summit meeting involving other leaders too.

U.S. Secretary of State Antony Blinken and Russian Foreign Minister Sergey Lavrov are to lay the groundwork for the summit at a meeting Thursday, according to Macron's office.

WHAT'S THE SITUATION ON THE UKRAINE’S EASTERN FRONT?

Heavy shelling has increased in recent days along the tense line of contact between Ukrainian forces and Russian-backed separatist rebels in Ukraine’s eastern industrial heartland of Donbas.

It's a war that began in 2014 after Russia annexed Crimea from Ukraine. The fighting has claimed at least 14,000 lives but had been largely quiet for a while.

Ukrainian military spokesman Pavlo Kovalchyuk said Ukrainian positions were shelled 80 times Sunday and eight times early Monday, noting that the separatists were “cynically firing from residential areas using civilians as shields.” He said Ukrainian forces weren’t returning fire.

In the village of Novognativka on the government-controlled side, 60-year-old Ekaterina Evseeva, said the shelling was worse than at the height of fighting.

“It’s worse than 2014,” she said, her voice trembling. “We are on the edge of nervous breakdowns. And there is nowhere to run.”

RUSSIAN TROOPS STAY IN BELARUS, ADDING TO FEARS

Russian troops who have been carrying out military exercises in Belarus, which is located on Ukraine's northern border, were supposed to go home when those war games ended Sunday. But now Moscow and Minsk say that the Russian troops are staying indefinitely.

The continued deployment of the Russian forces in Belarus raised concerns that Russia could send those troops to sweep down on the Ukrainian capital of Kyiv, a city of 3 million less than a three-hour drive away from the Belarus border.

UKRAINE PROJECTS CALM

Despite Biden’s assertion that Putin has made the decision to roll Russian forces into Ukraine, Ukrainian officials sought to project calm, saying that they aren’t seeing an invasion as imminent.

Defense Minister Oleksii Reznikov said Monday that Russia has amassed 147,000 troops around Ukraine, including 9,000 in Belarus, arguing that the number is insufficient for an offensive on the Ukrainian capital.

“The talk about an attack on Kyiv from the Belarusian side sounds ridiculous,” he said, charging that Russia is using the troops there to create fear.

Over the weekend at the Polish border, many Ukrainians were also returning home from shopping or working in the neighboring EU country. Some said they were not afraid and vowed to take up arms against Russia in case of an assault.

EU OFFERS TO ADVISE UKRAINE

Ukrainian Foreign Minister Dmytro Kuleba said Monday that the European Union has agreed to set up a military education advisory mission in his country.

Kuleba told reporters in Brussels after meeting with the bloc's foreign ministers that an agreement had been reached in principle to roll out the advisory training military mission.

“This is not combat forces. This is a new element in the cooperation between Ukraine and the European Union,” he said, adding that details about the mission are still being decided. “It is critical that we open this new page in our relations.”

The move could involve sending European officers to Ukraine’s military schools to help educate its armed forces. It’s likely to take several months to set up.

THE LATEST BRITISH WARNINGS

Britain’s defense secretary, Ben Wallace, urged Putin to turn away from military action and pursue diplomacy not just for the sake of Ukrainians but to prevent Russian deaths.

Russians knows the consequences of the past actions, including the invasion of Afghanistan and Russia’s invasion of Chechnya, he said.

“These are just two examples when too many young men returned home in zinc-lined coffins, and the government therefore urges President Putin for the sake of his own people, and even at this 11th hour, to rule out the invasion of Ukraine," he said.

Wallace told the House of Commons that Putin had continued to build up forces in the region. Russia has now massed 65% of its land combat power on the Ukrainian border, he said.

U.K. Foreign Secretary Liz Truss also warned on Twitter that “a Russian invasion of Ukraine looks highly likely.”

"The U.K. and allies are stepping up preparations for the worst-case scenario. We must make the cost for Russia intolerably high,” she said.

ITALY ASKS CITIZENS TO LEAVE UKRAINE

Italy has renewed calls to its citizens urging them to leave Ukraine.

Italian media have been carrying interviews with Italians in Ukraine who have indicated a reluctance to leave because they have businesses, including restaurants, or are married to Ukrainians.

Foreign Minister Luigi Di Maio said in Brussels that the Italian embassy in Kyiv is also carrying out rehearsals for evacuating its personnel in case the country needs to take that step.

For now the the embassy remains fully operative “because we believe in diplomacy and we want to give a clear signal of closeness to the Ukrainian people,’’ Di Maio said.