Wife of the commander of the Azov regiment, Denys Prokopenko, told The Associated Press that she had received a brief phone call from him, thanks to the mediation of the Red Cross.

He confirmed that he was alive and was being held prisoner in Russian - controlled territory, his wife, Kateryna, said.

Ukraine has said it hoped to bring the captured fighters home in a prisoner exchange, but Moscow has sent signals that some may be charged with war crimes.