At an extraordinary break from diplomatic etiquette, Pope Francis traveled to the Russian embassy in the Holy See on Friday to express his alarm over Russia’s invasion of Ukraine to Moscow’s ambassador.

According to Vatican spokesperson Matteo Bruni, the pope spent more than 30 minutes in the embassy.

“He went to voice his worry over the conflict,” Bruni said, omitting to elaborate on the visit or the dialogue.

Bruni would not comment on an Argentinian media report that the pope, 85, had offered the Vatican’s mediation. The ambassador, Aleksandr Avdeyev, denied this, according to the Rome correspondent of Russian TASS new agency.

Avdeyev told the RIA Novosti news agency that the meeting lasted about 40 minutes and that the pope expressed “great concern” about the humanitarian situation in Ukraine.

The ambassador was quoted as saying that the pope “called for the protection of children, the protection of the sick and suffering, and the protection of people.”

When contacted for comment by Reuters, the Russian embassy said the ambassador was not available.

The visit by a pope to an embassy to talk to an ambassador in a time of conflict is unprecedented in living memory.

Foreign envoys are usually summoned by the Vatican’s Secretary of State or meet with the pope in the Apostolic Palace.

In an interview with Reuters of Feb. 14, before the invasion, Ukraine’s ambassador to the Vatican, Andriy Yurash, said Kyiv would be open to a Vatican mediation of the conflict.

In a statement on Thursday, Vatican Secretary of State Cardinal Pietro Parolin said the Holy See hoped that those who hold the destiny of the world in their hands would have a “glimmer of conscience”.

World leaders have accused Russian President Vladimir Putin of a flagrant violation of international law by launching the biggest attack by one state against another in Europe since World War Two.

Francis made many appeals for peace in Ukraine before the invasion on Thursday, but has not spoken publicly since. He has proclaimed next Wednesday, Ash Wednesday, as a day of prayer and fasting for peace in Ukraine.

The Vatican announced separately on Friday that Francis would not be able to preside at the Ash Wednesday services because of an acute flare up of pain in his knee. He also will have to skip a trip to Florence this Sunday.