BEIRUT: Syrian opposition activists have posted a video of what they say is chlorine gas floating through the streets of a village, the first such footage of they say is a chemical weapon campaign by President Bashar al-Assad.
The village of Kfar Zeita, in the central province of Hama 125 miles (200 km) north of Damascus, has been the epicentre of what activists and medics call a two-month-old assault in which chlorine gas canisters have been dropped out of helicopters.
Damascus denies that forces loyal to Assad have used chlorine or other more poisonous gases and blames all chemical attacks on rebels fighting them in a three-year-old uprising.
Text accompanying the video, posted on Thursday by a user called Mustapha Jamaa, said it was filmed on Thursday in Kfar Zeita by the Revolution General Commission, an opposition group.
It showed green-yellow gas in a street. A man runs away from the gas cloud with a woman who is holding a cloth to her mouth. Another man in camouflage trousers and wearing a gas mask calls out for a car to assist the woman. A voice off screen says: "Chlorine gas bombing. Yellow smoke."
Reuters could not independently verify the authenticity of the footage. The video did not show an impact site or indicate where it was filmed.
A Reuters freelance photographer said he arrived at the scene of the attack an hour after a helicopter dropped the bomb.
"The smell of chlorine was very obvious. It smelt like vinegar, or bleach. I started to cough and hyperventilate. My eyes were burning," he said.
One of his photos showed the woman who was running away from the gas in the video. She was being treated with oxygen at a field hospital. "There were 70 wounded people," he said. "Those who were at the impact site fainted."
Activists said Kfar Zeita was attacked twice on Thursday, as well as the village of Al-Tamana'a in northwest Idlib province. There have been more than a dozen reported chlorine attacks in Syria since April 11.
The alleged attack came on the same day that Russia and China vetoed a resolution to refer the situation in Syria to the International Criminal Court for possible prosecution of war crimes and crimes against humanity.
Assad agreed with the United States and Russia to dispose of his chemical weapons after hundreds of people were killed in a sarin gas attack on the outskirts of the capital last August.
Chlorine is thousands of times less lethal than sarin but its use as a weapon is still illegal under a global chemical weapons convention that Syria signed.
Its use would also breach the terms of the deal with Washington and Moscow, itself now weeks behind schedule, with roughly seven percent of Assad's chemical arsenal still inside Syria.
Syria did not declare chlorine as part of its stockpile, further complicating the operation to rid Assad of chemical weapons.
The watchdog Organisation for the Prevention of Chemical Weapons (OPCW) is considering launching its own fact-finding mission to investigate the reports of chlorine gas attacks, sources told Reuters last month.
Syria's civil war started with a pro-democracy movement against Assad that armed itself following attacks by security forces on protesters.
The ensuing conflict has killed more than 160,000 people, a third of them civilians, and caused millions to flee.