Kyiv: At least four people were killed and 12 others sustained injuries in an overnight attack by the Russian troops against Ukraine's Kharkiv, regional Gov. Oleh Syniehubov said on Thursday.

Russia attacked Ukraine's second-biggest city with at least 15 drones, some of which were shot down by air defense.

Three rescuers were killed when Russia struck a multistory building damaged in an earlier strike. Six people were wounded at that location. Another 14-story building was hit by a drone, killing a 69-year-old woman.

Kharkiv has become a frequent target for Russian troops in recent weeks. The eastern city is close to the border with Russia and has been hit with both ballistic missiles and drones.

A recent massive missile attack that aimed to significantly damage Ukraine's energy infrastructure plunged most of Kharkiv into darkness, and the situation there is still being stabilized.

“Each manifestation of Russian terror once again proves that the country-terrorist deserves only one thing — a tribunal,” Ukraine' human rights chief, Dmytro Lubinets, published on Telegram in response to the attack. 

(With AP inputs)