At least 30 people were treated for breathing difficulties after a regime chlorine gas attack in the Damascus suburb of Eastern Ghouta, according to a Syrian civil defense agency on Tuesday.
Several children and women were among the victims of the attack in Hamuriye town on Monday, the White Helmets said in a statement.
The civil defense agency said two of its rescue workers were among the casualties.
Last month, a Syrian child was killed in a regime gas attack in Eastern Ghouta, prompting the Hague-based Organization for the Prohibition of Chemical Weapons (OPCW) to launch an investigation into the attack.
Eastern Ghouta has been under siege for the last five years, and humanitarian access to the area, which is home to some 400,000 people, has been completely cut off.
In the past eight months, Bashar al-Assad regime forces have intensified their siege on the region, making it nearly impossible for food or medicine to get into the district and leaving thousands of patients in need of treatment.
Hundreds have been killed by regime airstrikes in recent days.
Last month, the UN Security Council adopted a resolution calling for a 30-day cease-fire in Syria without delay.
