UK blames Assad regime after watchdog documents chlorine attacks

Reacting to the report, Britain and the United States blamed the regime of Syrian President Bashar al-Assad, which they said was the only party in the civil war with helicopters.

"The moderate opposition do not possess air capability power that could do this," U.S. State Department spokeswoman Marie Harf said. "This points to the conclusion that the Assad regime is responsible for the attacks. They are the ones with this helicopter capability," she added.

The Hague-based Organisation for the Prohibition of Chemical Weapons (OPCW) said its fact-finding team had concluded "with a high degree of confidence that chlorine, either pure or in mixture, is the toxic chemical in question" in dozens of attacks.

The report, a copy of which was obtained by Reuters, described from extensive testimony from witnesses how hundreds of people were hurt and many were killed by the chlorine gas, often at night.

It gave credibility to hundreds of videos from Syria showing the devices falling from helicopters, which only government forces are known to possess. The anti-Assad rebels use rockets and missiles, but no case has ever been reported of them dropping munitions from the air, or of them having commandeered a helicopter.

British Foreign Secretary Philip Hammond said in a statement that the report supports claims that the Assad regime "is continuing to use chemical weapons in Syria" after agreeing to give up a chemical-weapons program.

"The systematic and repeated use of chlorine in northern Syria and the consistent reports from witnesses of the presence of helicopters at the times of the attacks leave little doubt as to the Assad regime’s culpability," he said

Although chlorine is not a prohibited substance, its use as a chemical weapon is prohibited under the 1997 Chemical Weapons Convention, which Syria joined a year ago this week.

Chlorine was used in attacks on the villages of Talmanes, Al Tamanah and Kafr Zeta, all located in northern Syria, the OPCW's report said.

If inhaled, chlorine gas - a deadly agent widely used in World War One - turns to hydrochloric acid in the lungs, which can lead to internal burning and drowning through a reactionary release of fluid in the lungs.

The most attacks were in the village of Kafr Zita, where witnesses described 17 chlorine attacks, the report said, one of them as recent as Aug. 28, with dozens of casualties.

"In describing the incidents involving the release of toxic chemicals, witnesses invariably connected the devices to helicopters flying overhead," it said.

"When dropped, a piercing heavy, whistling sound — some comparing it to that of a fighter jet in a dive — would be heard before the barrel hit the ground."

The muffled sound of the impact and the damage caused "suggest that the devices were designed either to rupture on impact or carry a small improvised explosive charge," the report said.

In another village, Talmanes, witnesses in the OPCW report recalled two attacks with barrel bombs containing chlorine dropped from helicopters on April 21 and 24, killing a teenage girl and a seven-year old boy and injuring 200 others.

In five helicopter attacks in April and May in the village of Al Tamanah, witnesses said the barrels were dropped at night.

There were "more than 150 casualties, and eight of the most severely affected, mostly women and children, died from exposure to lethal doses of the toxic chemical," it said.

Assad agreed to hand over 1,300 tonnes of chemical weapons and destroy production and storage facilities last year under a deal that averted threatened U.S. military strikes.

The bulk of the chemicals have been destroyed on a U.S. ship and at commercial toxic-waste processing facilities. Damascus still has to destroy 12 hangars and underground weapons facilities and clarify a series of discrepancies in the list of poisonous munitions it filed with the OPCW.

Even as some of the chemical weapons were being destroyed abroad, attacks with toxic agents were being reported in Syrian villages, leading to accusations from Western governments that Assad had not fully declared his arsenal.

Syria agreed to destroy its chemical weapons a year ago following global outrage over a sarin gas attack in Ghouta, a suburb of Damascus, in August 2013 that killed hundreds - the worst attack of its kind for a quarter century.

The government and rebels blamed each other for that attack. Western powers blame Assad, and Russia says rebels were probably responsible.

After coming under attack while doing field work in Syria, where a civil war has killed more than 191,000 people, the team based its research on dozens of interviews with victims, physicians and witnesses. It also used video material, medical records and other evidence.

It did not say which side in the conflict had used chemical weapons in the battlefield.