Antonio Guterres, the UN secretary-general, has separately requested meetings with Russian President Vladimir Putin and Ukrainian counterpart Volodymyr Zelenskyy in their countries’ capitals to try to negotiate an end to the nearly two-month war in Ukraine.

UN spokesman Stephane Dujarric said on Wednesday that Guterres had sent letters to the UN missions of Russia and Ukraine, asking Putin to receive him in Moscow and Zelenskyy to welcome him in Kyiv.

“The Secretary-General said, at this time of great peril and consequence, he would like to discuss urgent steps to bring about peace in Ukraine and the future of multilateralism based on the Charter of the United Nations and international law,” Dujarric said in a statement.

In an Easter appeal, Guterres on Tuesday called for a four-day truce during the Orthodox Christian Holy Week to allow for civilian evacuations and the delivery of humanitarian aid to hard-hit areas.

“Humanitarian needs are dire. People do not have food, water, supplies to treat the sick or wounded or simply to live day-to-day,” Guterres said in New York.

Russia’s February 24 invasion of Ukraine has killed thousands of people and left more than 12 million in need of humanitarian assistance. Some five million have fled Ukraine.

Since starting what it called a “special operation to demilitarise Ukraine”, Russia has bombed cities to rubble and hundreds of civilian bodies have been found in towns after its forces withdrew from areas near Kyiv.

Moscow, which this week launched a full-scale offensive in Ukraine’s east, denies targeting civilians and says, without providing evidence, that the indicators of atrocities being committed had been staged.

Western countries and Ukraine accuse Putin of unprovoked aggression.

European Council President Charles Michel met Ukrainian President Volodymr Zelenskyy during a surprise visit to Kyiv on Wednesday, following visits by other Western leaders, including British Prime Minister Boris Johnson and European Commission President Ursula von der Leyen.