Ramzan Kadyrov, the leader of Russia's Chechnya region and an ally of Russian President Vladimir Putin, said Russian forces would on Tuesday completely take over the Azovstal steel works where Ukrainian defenders have been holding out in the besieged port of Mariupol.

"Today, with the help of the Almighty, we will ... take over Azovstal completely," Kadyrov said in an audio message on his Telegram channel.

Russia earlier called on Ukrainian forces and foreign fighters holed up in the Azovstal plant to lay down their arms by noon Moscow time (0900 GMT) if they wanted to live.