A chemical attack in Douma, the last rebel-held stronghold near Syria's capital, Damascus, has killed at least 70 people and affected hundreds, rescue workers have told.
The White Helmets, a group of rescuers operating in opposition-held areas in Syria, said on Saturday that most of the fatalities were women and children.
"Seventy people suffocated to death and hundreds are still suffocating," Raed al-Saleh, head of the White Helmets, told Al Jazeera, adding that the death toll was expected to rise as many people were in critical condition.
Al-Saleh said that chlorine gas and an unidentified but stronger gas were dropped on Douma.
"White Helmet volunteers are trying to help the people but all that we can do is evacuate them to another area by foot because most of the vehicles and centres went out of service."
One member of White Helmets told that an entire family had suffocated to death as they hid in their cellar, trying to seek shelter from air raids and barrel bombs.
The US government has warned of a global response against Syria if reports of the chemical attack are confirmed.
The Syrian government, however, is calling it a fabrication, dismissing talk of the Syrian army using poisonous gas as "farcical".