Ukrainian President Volodymyr Zelensky listens during a joint press conference with Estonian Prime Minister after their meeting in Zhytomyr on April 24, 2023. AFP
Zelensky reported the strike on a local history museum in Kupiansk, a city near the frontline in the northeast, and gave the toll.
"There are still people under the rubble," Zelensky said on Telegram and posted a video of people in military uniform walking through the rubble of a partly destroyed building with its windows shattered.
Russia is "killing Ukrainians with absolutely barbaric methods," he said, accusing Moscow of "doing everything to destroy us completely. Our history, our culture, our people."
Ukraine regained Kupiansk, a key rail hub in northeastern Ukraine, in September.
As fear mounted that Russia may be pushing to retake the city, Ukraine ordered vulnerable residents to evacuate at the beginning of March.