Staff at the Russian-controlled Zaporizhzhia nuclear power plant in southern Ukraine have been detained and tortured by Moscow's forces, the president of Ukraine's nuclear energy agency told AFP in an interview Friday.

"A regime of police harassment of personnel was gradually established" following the Russian takeover, Petro Kotin said.

He described the situation at the plant now as "very difficult," citing "torture" of staff and "beatings of personnel".

Some 200 staff members have been detained and two among the plant's personnel were beaten to death, he added.