Russia's defence ministry said on Tuesday that more than 250 Ukrainian fighters holed up in Mariupol's Azovstal steel plant had surrendered.

"Over the past 24 hours, 265 militants have laid down their arms and surrendered, including 51 seriously wounded," the ministry said, following an earlier report from Russian-backed separatists that 256 fighters had surrendered.

The defence ministry said that those who needed medical treatment were sent to a hospital in Novoazovsk, a town in eastern Ukraine.

Ukraine's military said on Tuesday it was working to evacuate all remaining troops from their last stronghold in the besieged port of Mariupol, ceding control of the city to Russia after months of bombardment.

(Reporting by Reuters; editing by Guy Faulconbridge)