Russia “categorically rejects” allegations of war crimes over the bombing of four hospitals and two schools in Syria on Monday.
As many as 50 people, including 12 children, have been killed in missile attacks on three separate hospitals in northern Syria.
Syrian President Bashar al-Assad has said that he plans to retake “the whole country”, despite a renewed effort from the international community to push for peace.
The Syrian government carried out a policy of extermination against thousands of detainees at prisons across the country, say investigators from the UN Human Rights Council.
Russia has begun air strikes against rebel positions within Syria, with the first target near the western city of Homs, US defence officials say.