The defence ministry said the fighters were mostly French mercenaries and the building was destroyed, with more than 60 people killed. It did not provide evidence, and Reuters could not verify the claims.
Local officials in Kharkiv said two Russian missiles struck a residential area in the centre of the city on Tuesday, injuring 17 people, two of them seriously, and badly damaging homes.
The French foreign ministry did not immediately respond for comment.
(Reporting by Reuters; Editing by Mark Heinrich and Alistair Bell)
