Chemical weapons such as chlorine have likely been used in a "systematic manner" in Syria, according to a report by a team from the world's watchdog investigating alleged attacks there.
The Organisation for the Prohibition of Chemical Weapons (OPCW) mission said evidence "lends credence to the view that toxic chemicals, most likely pulmonary irritating agents such as chlorine, have been used in a systematic manner in a number of attacks," according to a copy of the report obtained by AFP.
President Bashar al-Assad's regime and rebels have both accused the other of using chemical agents, including chlorine, in the bloody uprising that began in March 2011 and in spite of Damascus promising to hand over all its chemical arms.
The OPCW team probing the allegations was attacked with a roadside bomb and gunfire on May 27, preventing them accessing the site of an alleged attack in the village of Kafr Zeyta.
"The attack on the team and the resulting denial of access prevents it from presenting definitive conclusions," the report added.
Nevertheless, the allegations "cannot be dismissed as unconnected, random, or of a nature attributable to purely political motives," the report said.
Despite not being able to visit the alleged site of the chlorine attack, OPCW officials spoke to doctors in Kafr Zeyta "and obtained their verbal medical reports relating to the treatment of individuals allegedly affected by exposure to chlorine."
The team also saw video footage of the alleged attack and of alleged munitions used in the attack, some of which remained intact.
The report noted that chlorine is a widely available chemical, that is non-persistent and so conclusively proving its use is "a challenging task".
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Syria has set up a committee to investigate further allegations of chemical attacks, the report said, with Damascus claiming to have captured chemicals from rebels, who had also seized a chlorine-producing plant 40 kilometres (25 miles) from Aleppo.
Syria has already shipped out 92 percent of its stockpile of chemical weapons under the terms of a UN-backed and US-Russia brokered deal agreed last year.
However, eight percent of its stockpile remains at one site and cannot be taken to Latakia port because of the security situation.
The chlorine probe came after France and the United States alleged that Assad's forces may have unleashed industrial chemicals rebel-held village in recent months.
Syria did not have to declare its stockpile of chlorine -- a weak toxic agent that can be considered a chemical weapon if used offensively -- as part of the disarmament deal as it is widely used for commercial and domestic purposes.
Danish and Norwegian ships are to take all of Syria's chemicals from Latakia port to a US ship for destruction at sea, along with sites in Finland, the US and Britain, by a now-impossible June 30 deadline.
The deal was reached after a sarin nerve gas attack in a rebel-held Damascus suburb killed around 1,400 people. Damascus agreed to hand over its chemical arsenal after the US threatened airstrikes against Assad in response.
The report from the watchdog's Technical Secretariat noted that a ceasefire had been agreed between the regime and rebels on the day of the May 27 visit.
Despite the attack on the OPCW team that day, in which a car was destroyed but no one was seriously hurt, the report said that "while field visits are not envisaged for the immediate future, these remain an option."