Ukrainian President Volodymyr Zelenskyy said a Russian guided aerial bomb hit a blood transfusion center in the town of Kupiansk in eastern Kharkiv region late on Saturday.

"There are dead and wounded," he said on his Telegram channel. Reuters could not immediately verify the report. Kupiansk is a railway hub fewer than 10 miles from the front.

Zelenskyy said rescue workers were extinguishing a fire at the scene and described the strike as a "war crime." He did not say how many people were killed or wounded.

Russia denies deliberately targeting civilians in a full-scale invasion that has killed thousands of people, uprooted millions, and destroyed cities.