Russian forces staged a “massive” drone attack on Sunday on Kharkiv, Ukraine’s second-largest city, killing four people and injuring several others, officials said.

“There is a massive attack on Kharkiv,” Mayor Ihor Terekhov wrote on the Telegram messaging app.

Terekhov said four people had been killed, including one person whose body was recovered from under rubble.

Regional Governor Oleh Syniehubov said 12 people were injured, including two children aged 11 and 12.

Fifteen strikes were recorded in six areas of the city in northeastern Ukraine.

Kharkiv, located 30 km (18 miles) from the Russian border, withstood Russian attempts to capture it early in the more than 3-1/2-year-old war and has since been a frequent target of attacks.

The governor of Dnipropetrovsk region, farther south, said two people were killed in a Russian strike on the town of Marhanets.