A Russian drone strike on Kharkiv, Ukraine's second largest city, killed at least seven people overnight, including three children, Kharkiv region governor Oleh Syniehubov reported on Saturday.

He said the Iranian-made Shahed drone hit civilian infrastructure in the Nemyshlyan district on the city, causing a massive fire that burned down 15 private houses.

Interior Minister Ihor Klymenko said more than 50 people had been evacuated and that emergency workers had contained the blaze by Saturday morning.

The Ukrainian air force said air defense systems destroyed 23 out of 31 Iranian Shahed drones launched by Russia overnight. The drones primarily targeted the northeastern Kharkiv region and the southern province of Odesa, the statement said.

Odesa regional governor Oleh Kiper said four people were injured there by the overnight drone attacks.