HRABOVE, Ukraine (AP) — A refrigerated train carrying Malaysia Airlines victims' bodies pulled away Monday from a rebel-held town in eastern Ukraine, one small step forward in easing the agony of their grieving families.

In an emotional inspection hours earlier, Dutch experts had called for a full forensic sweep of the Flight 17 crash site and told the armed separatists controlling the area that the train must be allowed to leave as soon as possible.

Four days after someone shot the Boeing 777 out of the sky, killing 298 people, pressure was growing on Russian President Vladimir Putin to rein in the insurgents and allow a full-scale investigation into the downing of the plane. The U.S., Ukraine and others say Moscow has armed the rebels, a charge Russia denies.

In Washington, President Barack Obama demanded that international investigators get full access to the crash site and accused the separatists of removing evidence and blocking investigators.

"What exactly are they trying to hide?" Obama asked, a day after the U.S. presented what it called "powerful" evidence that the rebels had shot down the plane with a Russian surface-to-air missile.

A team of international observers at the crash site suggested that some of the evidence may have been tampered with.

At the biggest of the incident sites on Monday, "we did not see any perimeter security in the place," OSCE spokesman Michael Bociurkiw told reporters in Donetsk. The monitors observed that one of the largest pieces of debris "had somewhat been split or moved apart."

On an earlier visit to one of the smaller impact sites observers had also witnessed apparent tampering. "When we were leaving, we observed workers there hacking into the fuselage with gas-powered equipment," Bociurkiw said.

At the U.N. in New York, the Security Council was voting later Monday on an Australia-proposed resolution demanding international access to the crash site and a cease-fire around the area. Australian Prime Minister Tony Abbott said his country would view a Russian veto of the resolution "very badly," adding that "no reasonable person" could object to its wording.

Fighting flared again between the separatists and government troops in the eastern rebel-held city of Donetsk, just 50 kilometers (30 miles) to the west of the crash site. City authorities said battles took place Monday near the town's airport. An AP reporter heard several explosions and saw smoke rising from that direction.

After the train with the bodies left the town of Torez, two military jets also flew overhead and black smoke was seen rising in the distance.

Fighting began in mid-April in eastern Ukraine after Russia annexed Ukraine's southern Crimean Peninsula a month earlier.

There is great concern in the Netherlands about the bodies, since 192 of the plane's 298 victims were Dutch and another was Dutch-American. Dutch Prime Minister Mark Rutte said Monday that repatriating the bodies was his "No. 1 priority."

An Associated Press reporter saw the train with the bodies leaving Torez, a rebel-held town 15 kilometers (9 miles) from the plane crash site, and overheard rebels saying it was heading for the rebel-held town of Ilovaysk. The Ukrainian government later said the train was eventually heading to a crisis center in the government-controlled eastern city of Kharkiv.

In farm fields near the eastern village of Hrabove, Peter van Vliet, leader of the group from the Dutch National Forensic Investigations Team visiting Ukraine, said seeing the crash site gave him goose bumps despite the heat. Workers recovered more bodies from the site Monday, bringing the total to 282 bodies, according to Volodymyr Groisman, Ukraine's deputy prime minister.

The Dutch team — which specializes in victim recovery and identification — saw some victims' remains still rotting in the fields of the crash site. They also inspected piles of passenger luggage, suggesting that they be put in a container and shipped out.

At the Torez train station, the Dutch investigators stood for a moment with their heads bowed and their hands clasped before climbing aboard to inspect the train cars, surrounded by armed rebels.

AP journalists said the smell of decay was overwhelming at the Torez train station and many with the inspectors wore masks or pressed cloths to their faces on the sunny, 84 degree Fahrenheit (29 degrees Celsius) day. A Ukrainian train engineer told The Associated Press that a power outage had hit the rail cars' refrigeration system for several hours overnight.

In Kharkiv, another team of international experts arrived, including 23 Dutch, three Australians, two Germans, two Americans, and one person from the U.K.

Malaysia's prime minister said the rebels agreed to hand over both black boxes from Flight 17 to Malaysian investigators in Ukraine later Monday.

The U.S. evidence that the rebels were involved in downing the plan included video of a rocket launcher, one surface-to-air missile missing, leaving the likely launch site; imagery showing the firing; phone calls claiming credit for the missile strike and phone recordings said to reveal a cover-up at the crash site.

"A buildup of extraordinary circumstantial evidence ... it's powerful here," said U.S. Secretary of State John Kerry. "Russia is supporting these separatists. Russia is arming these separatists. Russia is training these separatists."

Putin lashed out against the criticism Monday, accusing others of exploiting the downing of the plane for "mercenary objectives."

Putin said Russia was doing everything possible to allow a team of experts from the International Civil Aviation Organization, a U.N. agency, to investigate the scene. He again criticized Ukrainian government authorities in Kiev, saying they had reignited the fighting with the rebels after a unilateral cease-fire expired without progress on peace talks.

"If fighting in eastern Ukraine had not been renewed on June 28, this tragedy would not have happened," Putin said. "Nobody should or does have a right to use this tragedy for such mercenary objectives."

The head of counterintelligence for Ukraine's SBU security service, Vitaliy Najda, has said the Buk missile launchers came from Russia and called on Russia to supply the names of the service personnel "who brought about the launch of the missile" so they could be questioned. He said the rebels could not have operated the sophisticated weapon without Russian help but did not provide specific evidence for his claim.

In Moscow, Russian officials offered evidence Monday to counter U.S. claims that the rebels were responsible for shooting down the jet. The Defense Ministry showed photos they said proved that Ukrainian surface-to-air systems were operating in the area before the crash — nine times alone on Thursday, the day the plane was brought down.

Russian officials also said they had evidence that a Ukrainian Su-25 fighter jet had flown "between 3 to 5 kilometers (2 to 3 miles)" from the Malaysia Airlines jet.

"(The plane) is armed with air-to-air R-60 rockets, which can hit a target from a distance of up to 12 kilometers (7 miles) and guaranteed within 5 kilometers (3 miles)," said the chief of Russia's General staff, Andrei Kartopolov.

The defense ministry officials also insisted that Russia had not given the rebels any surface-to-air missiles and added they have no evidence that any missiles were launched at all. They asked the U.S. to share any satellite images of the launch.

In the Netherlands, victims' families were being consoled Monday by the Dutch royals.