Zelenskiy described the attack on the town as "very fierce and absolutely calculated".

"These were peaceful people, ordinary people," Zelenskiy said in his nightly video address.

"On the market, a (grain) elevator, a petrol station, a bus station and on a residential building. At this time, the list of dead stands at 10, with many injured."

Kyrylo Tymoshenko, deputy head of Zelenskiy's office, had earlier denounced the attack in a posting on the Telegram messaging app, accompanied by video footage of buildings in flames.

"Terrorists are inhuman," Tymoshenko wrote. "And they will be held to account for it."

Kurakhove is in Donetsk region, which has seen some of the heaviest fighting since Russia sent troops into Ukraine on Feb. 24.

In his video message, Zelenskiy also said that four policemen had been killed by a Russian mine while engaging in work to stabilise the energy grid in southern Kherson region. Four policemen were being treated for injuries.

Russia denies deliberately attacking civilians but cities across Ukraine have been pummelled by Russian forces.

(Reporting by Pavel Polityuk and Ron Popeski, Editing by Timothy Heritage and Cynthia Osterman)