François Hollande, the French president, on Sunday declared the Syrian leader had continued to use chemical weapons on the front line, though he added definite proof had not yet been established.
Officials are examining attacks on at least three towns in the last week where credible reports point to the use of chlorine gas, leaving dozens of people seeking treatment for the symptoms of poisoning.
While the Syrian regime has handed over 80 per cent of its declared chemical weapons stockpile for destruction under UN supervision, the attacks appear to show Assad’s regime is continuing to use poison against its own civilians.
“We have a few elements of information but I do not have the proof,” Mr Hollande said. “What I do know is what we have seen from this regime is the horrific methods it is capable of using and the rejection of any political transition.”
Gas attacks are seen as a particularly effective tool in sparking panic and fear in rebel-held areas. On Sunday, Laurent Fabius, the French foreign minister, indicated intelligence reports on the attacks were being scrutinised, stating his officials received “indications” of recent chemical attacks that were still being verified.
American and British officials are thought to be currently examining video footage of Chinese manufactured chlorine gas canisters rigged with explosive detonators hitting the town of Kafr Zita near Hama.
Activists said the gas was used during fierce fighting when regime troops appeared to be losing control of the strategic town of Khan Sheikhoun.
Since the initial attack on April 11, there have been at least two more chlorine related incidents in the rebel region.
Two separate attacks were reported last week at Tamanah in Idlib province and Zahraa near Homs. Last month credible reports of gas attacks emerged from Harasta and Jobar, both near Damascus.
While chlorine is not listed as a banned chemical agent in recognition of its wide range of industrial uses, its use as a weapon of war is prohibited under the 1925 Chemical Weapons Convention.
It was first deployed 99 years ago by German forces during the second Battle of Ypres during an offensive to overrun the Anglo-French trenches, costing at least 30,000 lives.
“Chlorine was a pretty good chemical weapon to use in 1915 to achieve battlefield advantages and while it has fallen pretty far down the schedule and lists of most dangerous gases in 2014 it remains an effective choice in certain places in Syria,” said Hamish de Bretton-Gordon, a director of SecureBio consultancy and a former commander of the British Army’s chemical readiness forces.
“The evidence from Kafr Zita is pretty compelling and is certainly being examined very carefully by officials.”
In response to the rebel accusations, Damascus has blamed the al-Qaeda linked Jabhat al-Nusra, claiming it in fact used the gas.
Eliot Higgins, a British blogger known as Brown Moses, who follows attacks in Syria, believes the regime’s explanation does not stand up as the bomb was dropped from a helicopter. “As reports claim a helicopter dropped the bomb, it seems highly unlikely Jabhat al-Nusra would have been operating a helicopter,” he said.
Mr Gordon believes that the regime has already got rid of the declared stockpile under its direct control but that the 20 per cent of the arsenal still to be shipped under a UN accord signed last year would not be moved by an April 30 deadline as rebel forces control access points to the bases where it is stored.
A recent SecureBio report warned the continued use of any type of chemical weapon in Syria and a failure to ship the entire stockpile was triggering increasing efforts by al-Qaeda linked groups to obtain chemical materials.
The risk of an mass attack in the Middle East by Jihadists based in Syria remained high.
Photo: A child cries as he sits on a bed with others in Kfar Zita hospital following an alleged gas attack in the town Photo: AP