Russian President Vladimir Putin told the visiting UN chief Tuesday that he still has hope for negotiations to end the conflict in Ukraine.

"Despite the fact that the military operation is ongoing, we still hope that we will be able to reach agreements on the diplomatic track," Putin told UN Secretary-General Antonio Guterres, who was visiting Moscow, in televised remarks.

"We are negotiating; we do not reject (talks)."

Sitting across from Guterres at a long table at the Kremlin, Putin said efforts at talks with Ukraine had been derailed by claims of atrocities committed by Russian forces in the town of Bucha outside Kyiv.

"There was a provocation in the village of Bucha, which the Russian army had nothing to do with," Putin said. "We know who prepared this provocation, by what means, and what kind of people worked on it."

Ukraine had proposed an international agreement whereby other countries would guarantee its security. In return, Kyiv would not join NATO or host foreign military bases and become a neutral, non-nuclear state. The talks between Ukraine and Russia in Turkey stalled after the discovery of civilian bodies in areas near Kyiv previously occupied by Russian forces.

Putin told Guterres he was "aware of your concerns about Russia's military operation" in Ukraine and ready to discuss it, but said the Ukraine issue arose after the 2014 "unconstitutional coup" in Kyiv and people in Donbas remained under blockade and military pressure even after the Minsk agreements on a peaceful settlement were reached.

Guterres reiterated his call from an earlier meeting with Russian Foreign Minister Sergei Lavrov for Moscow and Kyiv to work together with the UN to set up aid and evacuation corridors to help civilians in Ukraine.

He said that to resolve the situation in Ukraine's Mariupol, the UN is ready to fully mobilize its logistical capabilities and human resources, working together with the International Committee of the Red Cross (ICRC) as well as the Russian and Ukrainian armed forces.

The UN chief's spokesman Stephane Dujarric said Putin had agreed "in principle" to the UN and the ICRC being involved in evacuating civilians from the Azovstal steelworks in the port city of Mariupol.

"Follow-on discussions will be had with the United Nations Office for the Coordination of Humanitarian Affairs and the Russian Defense Ministry," Dujarric said in a statement after the meeting between Guterres and the Russian president.

Earlier on Tuesday, Putin told Turkish President Tayyip Erdogan that there were no military operations underway in Mariupol and that Kyiv should "take responsibility" for the people holed up in the Azovstal plant.

Ukraine on Monday appealed for the UN and the ICRC to be involved in the evacuation of civilians from Azovstal.

Before his trip to Moscow, Guterres met Erdogan on Monday in the Turkish capital Ankara. The UN chief is expected to meet Ukraine President Volodymyr Zelenskyy in Kyiv on Thursday.

(With input from agencies)

(Cover: Russian President Vladimir Putin (L) and UN Secretary-General Antonio Guterres hold a meeting at the Kremlin, Moscow, Russia, April 26. /CFP)