WARSAW, Poland (AP) — Catholic Church authorities in eastern Poland denounced nationalist views Wednesday and apologized after a radical extreme-right organization held a Mass in a regional cathedral.

Father Andrzej Debski, a spokesman for the church authorities in Bialystok, said the apology came after believers complained that a Mass was held in Bialystok Cathedral for the extreme-right National-Radical Camp, or ONR, celebrating its 82 years on April 16.

Founded in 1934, the ONR was built on Italian fascism and has promoted anti-Semitic ideas.

The Bialystok Curia "apologizes to all who feel hurt by the behavior of ONR members in Bialystok Cathedral," said a statement posted on its website. "The Curia assures that the church in Bialystok region is non-party and nationalism is alien to it."

Debski said the cathedral rector consented to the ONR anniversary Mass there, led by a priest of their choice, but the rector had failed to seek the approval from his superiors.

A few hundred ONR members, brandishing national and ONR flags, lined the church's aisle. Debski told The Associated Press that some people complained the priest's speech "was not in line with the spirit of the Gospels."

ONR members, mostly young people, then marched in Bialystok, chanting "Down with the European Union!" and "Great Catholic Poland!"

The ceremony has also been criticized by human rights activists, lawmakers and Facebook users.

The priest, Father Jacek Miedlar, known for his radical views, has been banned by the church from making any public statements.

Prosecutors are also investigating the situation.