At least 10 people have been injured when the centre of Ukraine's second city, Kharkiv, was hit by Russian rocket fire, local officials say.
The president's top aide said the attacks were revenge for Ukrainian success on the battlefield.
Rockets hit a children's arts centre and a school, as well as private homes, wounding at least ten people, including three children, Kharkiv mayor Ihor Terekhov wrote on Telegram on Friday.
Ukraine's presidential chief of staff Andriy Yermak said the attack was revenge for the success of Ukraine's armed forces, an apparent reference to a recent counter-attack in nearby areas which Ukraine says led to the recapture of over 20 settlements.
"For every success of Ukraine's armed forces, for every victory, Russians... answer with strikes on innocent people," Yermak wrote on Telegram, confirming that children were among the wounded.
"Russia is a terrorist state... you will answer (for this), and you almost certainly won't be able to hide anywhere," he wrote.
In another reported attack a Russian air strike hit a hospital in Ukraine's northeastern region of Sumy, destroying the building and wounding people, the region's governor says.
"Russian aviation, without crossing the Ukrainian border, fired at a hospital. The premises were destroyed, there are wounded people," the official, Dmytro Zhyvytskyi, said on Telegram on Friday.
The hospital is located in the Velyka Pysarivka district, which borders Russia, he said.
Russia denies targeting civilians.