Ukrainian officials say three children were among those killed in the central city of Vinnytsia.
Russian missiles have struck the central city of Vinnytsia, killing at least 20 people including three children, Ukrainian officials say.
Ninety more were reported wounded in the attack, to the south-west of the capital Kyiv and far from any front lines in the conflict.
Three Russian missiles hit an office block and damaged residential buildings.
Ukrainian President Volodymyr Zelensky called it “an open act of terrorism”.
The missiles hit the car park of the nine-storey office block at around 10:50 (0750 GMT), Ukraine’s State Emergency Service said. Residential buildings were also hit in the centre of Vinnytsia, which has a population of around 370,000.
The Russian defence ministry, which denies targeting civilians, has yet to comment on the strike.
The Ukrainian presidency said the attack had come from Kalibr cruise missiles launched from a submarine in the Black Sea.
A senior regional emergency service official told local TV that there was “probably no chance of finding anyone who survived” the attack.
“Every day, Russia kills civilians, kills Ukrainian children, carries out missile attacks on the civilian facilities where there is no military target. What is this, if not an open act of terrorism?” Mr Zelensky said in a statement on social media.
The attack came as EU foreign and justice ministers were due to meet in The Hague for a conference on alleged Russian war crimes.
Ukrainian Foreign Minister Dmytro Kuleba accused Russia of committing “another war crime” with the attack on Vinnytsia.
“We will put Russian war criminals on trial for every drop of Ukrainian blood and tears,” he wrote.