Russia's defense ministry said if Ukrainian forces still fighting in Mariupol lay down their arms starting at 6 a.m. Moscow time (0300 GMT) on Sunday, their lives will be spared, Tass news agency said.

Russia said earlier it had cleared all urban areas of resistance in Mariupol. It said the remaining fighters in the besieged port city – who it says are both Ukrainian and foreign – are blockaded in the Azovstal steelworks.

Tass quoted Colonel-General Mikhail Mizintsev, director of the Russian National Center for Defense Management, as saying Moscow's offer was prompted by "the catastrophic situation" in the plant as well as "purely humane principles."

He added: "We guarantee that the lives of all those who lay down their arms will be spared." Under the terms of the proposed deal, the remaining defenders in the plant would leave between 6 a.m. and 1 p.m. Moscow time, without weapons or ammunition.

There was no immediate reaction from Kyiv to the offer.