Denis Pushilin, leader of the self-proclaimed Donetsk People's Republic, said that a court would decide the fate of the Ukrainian fighters who had "surrendered" at the Azovstal steel plant in Mariupol, a local media outlet reported on Wednesday.

Russia said earlier that a total of 959 Ukrainian fighters, including 80 wounded, had surrendered from the bunkers and tunnels below the Azovstal steelworks since Monday.

The main commanders inside the plant had yet to surrender, DAN news agency quoted Pushilin as saying. 

Although Russia and Ukraine have conducted several prisoner exchanges, it is unclear how these surrenders will be treated.

The Kremlin has guaranteed that all would be treated "in accordance with international standards," but Russia's lower house of parliament, the State Duma, is considering to ban the exchange of Russian servicemen for members of Ukraine's ultra-nationalist Azov regiment, which made up a large part of the fighters defending Mariupol.