Amnesty International says it has collected "gruesome evidence of civilian deaths and casualties" inflicted in recent days by both pro-Russian separatists and Ukrainian forces in eastern Ukraine.
The rights group accused both sides of violating international humanitarian law with attacks in the rebel-controlled city of Donetsk and "indiscriminate shelling of homes and streets" in the government-controlled town of Debaltseve.
John Dalhuisen, Amnesty International's Europe and Central Asia director, said on February 2 that the evidence "reveals the horror of the bloodshed suffered by civilians, who are being killed and injured because both sides are firing unguided rockets and mortars in heavily populated areas."
Kyiv, NATO, the United States, and the European Union say Russia is sending troops and heavy weaponry into eastern Ukraine to support the separatists.
The United Nations says more than 5,100 people have been killed in the war since fighting began in April.
Russia denies it has troops or weaponry in eastern Ukraine, despite growing evidence to the contrary.