At least 20 civilians were killed and dozens wounded on Thursday in a Russian cruise missile strike on the central Ukrainian city of Vinnytsia by a submarine in the Black Sea, Ukrainian officials said.

Video footage and photographs from the city, which is far from frontlines, showed thick black smoke billowing out of a tall building after one of the deadliest single strikes on a civilian target since Russia invaded on February 24.

Three children were among the dead, officials said. One photograph posted online showed an overturned pram lying on the pavement, a covered body beside it. The twisted remains of burnt-out cars and smouldering rubble lay in the street.

Ukraine’s military said Vinnytsia, a usually quiet city 200 km (125 miles) southwest of Kyiv, was hit by three Russian Kalibr cruise missiles fired from an unnamed submarine, and that Ukrainian forces had shot down two others.

Police said the wounded included about 50 people who were seriously hurt and that 15 others were unaccounted for.

“Cruise missiles hit two community facilities, houses were destroyed, a medical centre was destroyed, the cars and trams were on fire,” President Volodymyr Zelenskiy said.

“This is the act of Russian terror … 20 people died as of now,” he said in a remote address to an international conference aimed at prosecuting war crimes committed in Ukraine.

The Russian defence ministry did not immediately comment on the reports from Vinnytsia. Russia, which invaded Ukraine on February 24, has denied deliberately targeting civilians and said its forces have not committed war crimes.

Ukrainian Deputy Defence Minister Hanna Malyar, at a briefing in Kyiv, described the attack as “more evidence of genocide”. Foreign Minister Dmytro Kuleba accused Russia on Twitter of committing “another war crime”.

A missile hit the car park of the nine-storey “Yuvelirniy” office block at around 10.50 a.m. (0750 GMT), the State Emergency Service said. Nearby residential buildings were damaged in the strike, and a huge fire started, it said.

A senior regional emergency service official said there was probably no chance of finding any more survivors under the rubble in Vinnytsia, which had a population of about 370,000 before Russia’s invasion.

The Kremlin says it is engaged in a “special military operation” to demilitarise Ukraine and root out what it regards as dangerous nationalists. Kyiv and its Western allies reject that as a false pretext for an unprovoked war of aggression.