Pope Francis, who has repeatedly called for peace in Ukraine, personally visited the Russian Embassy to the Vatican on Friday to express his concern about the war.

According to the media, the pope rode in a small white car the short distance to the embassy, located less than a quarter mile from the Vatican, despite “acute knee pain” that has forced him to cancel two public engagements next week.

“Pope Francis wanted to personally ask about the situation in Donbas and Ukraine,” Ambassador Alexander Avdeev told the Russian state news agency.

The Vatican spokesman, Matteo Bruni, said the pope spent just over half an hour at the embassy but wouldn’t say what the pope told the envoy, merely that “he went because he is concerned for the war.” Mr. Bruni declined to comment on whether Pope Francis had visited or would visit Ukraine's embassy to the Holy See. It is unusual for a pope, as a head of state, to travel to a foreign embassy for such a meeting.

On Thursday, Cardinal Pietro Parolin, the Vatican secretary of state, reiterated the pope’s previous appeals for peace in Ukraine, which he said had “acquired a dramatic urgency after the start of Russian military operations on Ukrainian territory.” The pope hasn’t condemned the Russian invasion or described it as an invasion.

Ukrainian Christians have in the past criticized Pope Francis for playing down Russian aggression in Ukraine by describing the fight against Moscow-backed separatists in the east as a “fratricidal” or civil conflict. In 2016, the leader of the Ukrainian Greek Catholic Church, Archbishop Sviatoslav Shevchuk, said that Ukrainian Catholics felt betrayed by a joint declaration signed by the pope and the Russian Orthodox Patriarch of Moscow that described the Ukraine conflict in such terms. Pope Francis replied that Archbishop Shevchuk was his friend and free to debate the statement.

The 2016 meeting was the first in history between a pope and an Orthodox patriarch of Moscow, and Francis has said he hopes to meet again with Patriarch Kirill this year. Russia’s ambassador to the Vatican said last week that the meeting could occur in June or July, at a location to be determined. The Vatican didn’t immediately reply when asked whether the war would affect plans for the meeting.