Russian drones hit residences early on Thursday in Kharkiv, Ukraine's second largest city, and three rescue workers were killed in a repeat strike at the site of the attack, the mayor and the regional governor said.
Kharkiv regional Governor Oleh Synehubov said the rescue workers were killed after they had arrived at the scene of the attack and a new strike occurred.
He said a total of four strikes had hit the city and the top floors of one apartment building had been damage.