Two Jesuit priests were killed in their apartment near Moscow's police headquarters, officials said Wednesday, in an attack that one religious leader condemned as a brutal murder.

As Russian officials launched an investigation, no information was immediately available about who had carried out the attack or what may have motivated it. Ties between the Vatican and the Russian Orthodox patriarchy have long been strained in Russia, but officials said it did not appear the rift was behind the killings.

The Rev. Igor Kowalewski, the general secretary of the Catholic Russian Bishops Conference, said the priests' bodies were found late Tuesday in an apartment on Petrovka street in downtown Moscow.

"They were brutally murdered," Kowalewski told The Associated Press.

Kowalewski said he was unaware of any threats against the priests: Otto Messmer, a Russian citizen, and Victor Betancourt, a national of Ecuador.

A Vatican spokesman, the Rev. Federico Lombardi, said the priests apparently had been killed with blunt objects.

The Vatican statement said it appeared that Betancourt, 42, was killed at the end of last week.

"He did not show up as usual to celebrate Mass on Sunday, and it was thought that he was sick," it said. Messmer, 47, returned to Moscow on Monday night after a trip to Germany, the Vatican said.

A fellow Jesuit, concerned that nothing had been heard from them, went to their residence and "found their lifeless bodies ... and told police," the statement said, adding that the head of the Jesuits, Adolfo Nicolas, has asked all members of the order to pray for the victims and their families.

Russia's Investigative Committee under the Prosecutor General's Office said the priests' bodies were found at an apartment owned by the Russian branch of the Society of Jesus, as the Jesuit order is formally known. The apartment building is located on the same street as the city police headquarters.

The committee said the victims apparently died of head injuries a day before, or even earlier. The apartment's door was open, but there was no immediate information about any valuables missing from the apartment, the committee said.

It said the priests seem to have been sharing a meal when they were attacked.

The Catholic Russian Bishops Conference said it had suffered a "grave loss."

"Two zealous pastors much loved by the faithful have been deprived of life," it said in a statement. It included prayers for the souls of the victims, prayers for the killers and a call that they be brought to justice.

The killings were reported a few hours before the head of the Russian Orthodox church met with a Catholic cardinal in France. Russian Orthodox Patriarch Alexy II offered his condolences over the priests' death during his meeting Wednesday with the archbishop of Paris, Cardinal Andre Vingt-Trois.

"It's our common duty to pray for their souls to rest in peace," he said, according to the Moscow Patriarchy.

The Russian Orthodox Church has accused the Vatican of poaching for converts in Russia. The Roman Catholic Church contends it is simply looking after its tiny flock in former Soviet nations, where Orthodoxy is the predominant Christian denomination.

But ties between the two churches have been steadily improving since Pope Benedict XVI succeeded the late Pope John Paul II in 2005.

Earlier this month, Benedict XVI cautioned Roman Catholic bishops in former Soviet republics against aggressive attempts to gain converts — a statement that could help assuage Russian concerns about alleged Catholic proselytizing.