At least 25 people were killed in a shelling attack in the Russian-held city of Donetsk, the Moscow-installed leader of the region said.
Denis Pushilin said a Ukrainian strike, which also injured 20 people, hit a busy market.
He said emergency services were working at the scene, and that information on the number of dead and wounded was still being collected.
There was no immediate comment from Ukraine on the incident.
Photographs published by Reuters news agency appeared to show destroyed shop fronts, as well as bodies lying in the street.
Donetsk city and parts of the wider region in eastern Ukraine were first seized by Russian-backed forces in 2014, and the area has been partially controlled by Moscow ever since.
The city is around 20km (12 miles) from the frontline. Areas near Donetsk city – including Mariinka and Avdiivka – have seen some of the fiercest fighting of late.
