Russia's state-run news agency reports that over 1,000 Ukrainian servicemen and mercenaries who had surrendered in the eastern Ukrainian city of Mariupol have been transferred to Russia for investigation.

Tass news agency cited a Russian law enforcement source on Wednesday.

The Ukrainian defenders were holed up at the Azovstal steel plant in Mariupol. They included Ukrainian troops, Azov battalion fighters and foreign mercenaries.

Tass reported that about 2,400 fighters surrendered at the Azovstal plant.

Russia and Ukraine had earlier agreed to exchange the bodies of 320 fighters in the southeastern region of Zaporizhzhia. A group of families of the Azov unit said that about a third of the 160 bodies were Azov battalion fighters.