A Russian air attack hit a school stadium in Ukraine's northeastern Kharkiv on Wednesday, injuring at least four children and three adults, officials said.

Two teenagers were hospitalised in serious condition, regional governor Oleh Synehubov said on the Telegram messenger.

The prosecutor's general office added that the school and nearby residential buildings were damaged in the attack.

Kharkiv, Ukraine's second largest city, and the surrounding region have long been targeted by Russian attacks but the strikes have become more intense in recent months, hitting civilian and energy infrastructure.

Russia denies targeting civilians but many have been killed and injured in its strikes during the 26-month-old full-scale invasion of Ukraine.

  - Reuters