Russian rockets have hit the eastern Ukraine town of Chasiv Yar, destroying a five-storey apartment building and killing at least 15 people.
Pavlo Kyrylenko, governor of the Donetsk region, said more than 20 people could be trapped in the rubble.
The Saturday night rocket assault is the latest in a recent burst of high-casualty attacks on civilian structures. At least 19 people died when a Russian missile hit a shopping centre in the city of Kremenchuk in late June and 21 people were killed when an apartment building and recreation area came under rocket fire in the southern Odesa region this month.
Russia has repeatedly claimed it is only hitting targets of military value in the war.
Mr Kyrylenko said the town of about 12,000 people was hit by Uragan rockets, which are fired from truck-borne systems.
Chasiv Yar is about 12 miles south-east of Kramatorsk, a city that is expected to be a major target of Russian forces as they grind west.
The Donetsk region is one of two provinces along with Luhansk that make up the Donbas region, where separatist rebels have fought Ukrainian forces since 2014.
Last week, Russia captured the city of Lysychansk, the last major stronghold of Ukrainian resistance in Luhansk.
Russian forces are raising “true hell” in the Donbas, despite assessments they were taking an operational pause, Luhansk governor Serhiy Haidai said on Saturday.
After the seizure of Lysychansk, some analysts predicted Moscow’s troops would take some time to rearm and regroup.
But Mr Haidai said: “So far there has been no operational pause announced by the enemy. He is still attacking and shelling our lands with the same intensity as before.”
He later said the Russian bombardment of Luhansk was suspended because Ukrainian forces had destroyed ammunition depots and barracks used by the Russians.
