The United Nations has accused both sides of committing war crimes in the battle for Aleppo that the government won in December.
In a new report, U-N investigators say Syrian government forces attacked civilians with chlorine gas in the city Aleppo last year.
It says the attacks took place in September and December as Syrian forces and their ally Russia were battling rebels for control of the northern city.
Citing eyewitnesses, doctors and video footage, the U-N Commission of Inquiry on Syria says it documented hundreds of civilian casualties from chemical bombs in September and December.
The inquiry accuses the rebels of firing shells indiscriminately at government-held areas and of using human shields.
A member of the inquiry, Carla Del Ponte, says she hopes those responsible will be put on trial.
