VATICAN CITY, Holy See -- The mayor of Kyiv has invited Pope Francis to the Ukrainian capital to "show his compassion", but the Vatican did not say Tuesday if the pontiff had agreed to go.

In a letter dated March 8 and viewed Tuesday by AFP, mayor Vitali Klitschko wrote that "the world religious leader's presence in person in Kyiv is key for saving lives and paving the path to peace in our city, country and beyond."

"We appeal to you, as a spiritual leader, to show your compassion, to stand with the Ukrainian people by jointly spreading the call for peace," he wrote in English.

A Vatican spokesman said in a statement that Francis had received Klitschko's letter "and is in solidarity with the suffering of the city, its inhabitants, those who had to flee and those called to manage it.

"He prays to the Lord that they will be protected from violence," Vatican spokesman Matteo Bruni said.

Bruni did not say whether the 85-year-old pope would accept or refuse the invitation to Kyiv, where on Tuesday Klitschko imposed a 35-hour curfew following fresh attacks by Russia on the capital.

As an alternative, Klitschko invited the pope to participate in a joint video conference, either pre-recorded or broadcast live, that he said could include Ukraine President Volodymyr Zelensky.

Since Russia invaded Ukraine on February 24, Francis has spoken out repeatedly against the violence. On Tuesday, Bruni repeated the pope's message from Sunday, in which he said "the unacceptable armed aggression must simply stop, before it reduces cities to graveyards."