At least 70 people were treated for breathing problems Tuesday in the Syrian city of Aleppo after what rescue workers say was a chlorine gas attack by government forces.
The Syria Civil Defense group said helicopters dropped several barrels containing chlorine on the opposition-held al-Sukkari neighborhood.
The Britain-based Syrian Observatory for Human Rights also reported a barrel bomb attack in the area, but could not confirm whether chlorine was involved.
Accusations of chemical attacks have been a fixture of the Syrian conflict with both the government and rebels blaming the other during the past five years.
International inspectors issued a report last month saying government forces and Islamic State militants had each carried out chemical attacks. United Nations experts said Tuesday more investigations are ongoing into alleged chemical attacks earlier this year, including in Aleppo.