A concentrated, 9-minute-long Russian drone attack on Ukraine`s second-largest city of Kharkiv on Wednesday killed 6 people and injured 64, including 9 children, Ukrainian officials said, writes Reuters.

The attack followed Russia`s 2 biggest air assaults of the war on Ukraine this week, part of intensified bombardments that Moscow says are retaliatory measures for Kyiv`s recent attacks in Russia.

A new wave of drone attacks on 4 city districts was reported early on Thursday by Kharkiv Mayor Ihor Terekhov, including a drone that landed in a school courtyard and smashed windows. There were no other reports of casualties or damage.

Elsewhere, 2 southern Ukrainian regions, Mykolaiv and Kherson, were left without electricity on Wednesday after Russian forces attacked an energy facility, the governors said.

Kharkiv withstood Russia`s full-scale advance in the early days of the war but has since been a regular target of drone, missile and guided aerial bomb assaults.

Prosecutors in Kharkiv region said on the Telegram messaging app that the death toll in Tuesday night`s incidents had risen to 6 as rescue teams pulled bodies from under the rubble. They said 3 people were still believed to be trapped.