Amnesty International says Russian air raids in Syria have killed hundreds of civilians and may amount to war crimes.
The rights watchdog said in a report on December 23 that some air raids attacked residential areas, striking homes, a mosque, a busy market, and medical facilities.
Such attacks may amount to war crimes, the report said, adding that it "is crucial that suspected violations are independently and impartially investigated."
Russia's Defense Ministry strongly rejected the allegations, saying the report was full of "cliches and lies."
Russia began its air campaign in Syria on September 30 to help Syrian President Bashar al-Assad, a Kremlin ally.
Moscow has repeatedly denied targeting civilians, saying it takes great care to avoid bombing residential areas.
It also denied using internationally banned deadly cluster bombs in Syria.
Amnesty, however, said it has gathered evidence, including photos and video footage, suggesting the Russians have used unguided bombs, including cluster munitions, in densely populated civilian areas.
The Syrian conflict has killed more than 250,000 people and forced millions to flee their homes since it broke out in March 2011.