Kyrylo Tymoshenko, deputy head of President Volodymyr Zelenskiy's office, said the building in the town of Beryslav in the Kherson region was hit as the family was preparing to celebrate the Orthodox Christian Christmas.
"People were preparing to celebrate Christmas together, but a cynical blow by the Russians killed them in their own home," Tymoshenko wrote on the Telegram messaging app.
He described the shelling as a base and mean attack that was carried out soon after Patriarch Kirill of Moscow, the head of the Russian Orthodox Church, called for a Christmas truce. Kyiv dismissed the appeal as a "cynical" trap.
Russia denies deliberately targeting civilians in what it calls its special military operation in Ukraine.
(Reporting by Pavel Polityuk, Editing by Timothy Heritage)
