More than 1,000 people including Ukrainian servicemen and foreign mercenaries who surrendered in Mariupol were sent to Russia for investigation, Russian news agency TASS reported Wednesday citing a law enforcement source.

"More than 1,000 people from Azovstal were brought to Russia. Law enforcement organs are working with them closely," the source was quoted as saying without giving details about what might happen next.

Kyiv did not immediately respond to the report. 

Russian defense ministry claimed "complete liberation" of the Azovstal steel plant in Mariupol on May 20.

Earlier this week, Ukrainian President Volodymyr Zelenskyy confirmed that more than 2,500 fighters who defended the plant were held in captivity by Russia.