Russia accused the Ukrainian military of deliberately striking a hospital in a Russian-held area of eastern Ukraine on Saturday in what it said was a war crime that killed 14 people and wounded 24 patients and medical staff.
There was no immediate response to the allegations from Ukraine. Reuters was not able to independently verify the report.
"A deliberate missile strike against a known functioning civilian medical facility is without doubt a serious war crime by the Kyiv regime," the defence ministry said.
"All those involved in the planning and execution of this crime will be found and held accountable."
Civilian and military medics had been working in the hospital for many months treating local people and soldiers, it said.
Ukraine and its Western allies have accused Russian forces of frequent war crimes in the conflict in which thousands of civilians have been killed and cities and towns pounded by artillery and air strikes. Russia denies targetting civilians.