Civilians in Syria's second city of Aleppo are suffering unthinkable atrocities, Amnesty International says.
A new report alleges that government forces and many rebel groups are committing war crimes on a daily basis.
The government has reportedly stepped up its bombardment of Aleppo in recent weeks in response to a rebel offensive.
President Bashar al-Assad categorically denied that barrel bombs had ever been used by his forces in aninterview with the BBC in February.
At least 10 people, including four children and teacher, were killed on Sunday when a barrel bomb hit a nursery school in the Saif al-Dawla district.
Local journalist Zaina Erhaim told the BBC on Monday that she heard the sound of children's screams and saw rescuers struggling to pull victims from the rubble.