Pope Francis has warned the leader of the Russian Orthodox Church not to be "Putin's altar boy" after the patriarch justified the Russian president's invasion of Ukraine.

The words of the leader of the Catholic Church carried in an Italian newspaper were some of the strongest yet used against the Orthodox ally of President Vladimir Putin as a supporter of his war that began with the invasion of Ukraine on Feb. 24.

On March 16 Vatican News had quoted Pope Francis saying to the Russian Patriarch: "The Church uses the language of Jesus, not of politics."

Francis denounced Kirill for endorsing Russia's stated reasons for invading Ukraine

The war has not only cut Russia off from the mainstream of humanity it has set the world of Orthodox churches on a collision course between its various churches and with the rest of Christianity.

The Italian newspaper Corriere della Sera, reported on May 3 that Francis said he spoke with Moscow Patriarch Kirill, long a key supporter of Vladimir Putin and now a cheerleader for his war.

The head of the Catholic Church had spoken for 40 minutes over Zoom with the leader of the biggest Orthodox Church and the biggest single member church of the Geneva-based World Council of Churches.

During the March 16 conversation, Francis said, Kirill has reeled off justifications for the war in Ukraine from a sheet of paper he was holding.

"I spoke to him for 40 minutes via Zoom," the Pope told Corriere della Sera. "The first 20 minutes he read to me, with a card in hand, all the justifications for war."

"I listened and told him: I don't understand anything about this," said the Pope. "Brother, we are not clerics of state, we cannot use the language of politics but that of Jesus."

"The Patriarch cannot transform himself into Putin's altar boy," Francis said.

The Russian Orthodox Church said the Pope's comments were "regrettable," in a statement Wednesday according to CNN.

'WRONG TONE'

"It is regrettable that a month and a half after the conversation with Patriarch Kirill, Pope Francis has chosen the wrong tone for conveying the contents of the conversation," said the Department of External Relations of the Russian Patriarchate.

"Such declarations do not contribute to establishing a constructive dialogue between the Roman Catholic Church and the Russian Orthodox Church which is particularly necessary at this time," the statement reads.

Also, on May 4 it emerged that the Patriarch is among the individuals who will be included in the proposed sixth round of European Union sanctions against Russia, according to two sources who have seen the full documents.

A European External Action Service document obtained by Politico showed that sanctions were proposed against in which he was described as "one of the most prominent supporters of the Russian military aggression against Ukraine" and someone who has helped boost Putin's rhetoric about the war, Newsweek reported.

The reported sanctions proposed against the patriarch came as the European Commission, the European Union's executive branch, announced one of its most serious moves yet against Russia for its assault on Ukraine: a ban on Russian oil.

At this stage names can be taken off or added at member state discretion, an EU Commission source said.

Russian Orthodox Church spokesman Vladimir Legoida said the sanctions were out of touch with "common sense," the Russian state news agency TASS reported.

"The more indiscriminate [these] sanctions become, the more they lose touch with common sense and the harder it becomes to reach peace, which is what the Russian Orthodox Church prays for at every service with the blessing of His Holiness the Patriarch, and assistance to all those affected by the Ukrainian conflict, only serve to affirm his words," Legoida said in a Telegram post on Wednesday.

"Only those completely ignorant of the history of our church can seek to intimidate its clergy and believers by compiling some lists," Legoida said.