Syria chemical weapons: finger pointed at jihadists

Whatever happened last week in the town of Khan al-Assal, west of Aleppo, it achieved something extraordinary in the Syrian civil war: unity among Washington, Moscow and Damascus.

All welcomed the rapid decision by Ban Ki-moon, the United Nations secretary-general, to investigate an alleged chemical attack that reportedly killed 26, including Syrian soldiers.

Unusually, the request for that investigation came from the Syrian regime, which claimed that Islamic jihadist rebels launched a chemical weapons attack. Since then, precious little evidence in any way has come from the area despite an awful lot of diplomatic noise around the world.

However a senior source close to the Syrian Army has given Channel 4 News the first clear account of what he claims is believed to have occurred on Tuesday. He is a trusted and hitherto reliable source who does not wish to be identified.

The Syrian military is said to believe that a home-made locally-manufactured rocket was fired, containing a form of chlorine known as CL17, easily available as a swimming pool cleaner. They claim that the warhead contained a quantity of the gas, dissolved in saline solution.

The source said that the town of Khan al-Assal has been in government control since March 13 but - like so much of the area - has been much fought over and parts of the area change hands with relative frequency. Rebel Sunni groups with al-Qaeda sympathies have been attacking the town, where the population is predominantly Shia.

The military's version of events is that the home-made rocket was fired at a military checkpoint situated at the entrance to the town. The immediate effects were to induce vomiting, fainting , suffocation and seizures among those in the immediate area.

A second source - a medic at the local civilian hospital - said that he personally witnessed Syrian army helping those wounded and dealing with fatalities at the scene. That Syrian soldiers were among the reported 26 deaths has not been disputed by either side.

The military source who spoke to Channel 4 News confirmed that artillery reports from the Syrian Army suggest a small rocket was fired from the vicinity of Al-Bab, a district close to Aleppo that is controlled by Jabhat al-Nusra - a jihadist group said to be linked with al-Qaeda and deemed a "terrorist organisation" by the US.

The American and independent weapons analysts do not believe that the regime or rebels used advanced chemical weapons last week, after studying initial intelligence reports and video coverage of survivors on state-run television.

However, they suspect that the victims were deliberately exposed to a "caustic" agent such as chlorine. This does not count as a chemical weapon, under terms laid down by international treaties, but as an improvised chemical device would represent a major escalation in the conflict.

Satellite intelligence analysed in Washington does not indicate a major missile launch at the time of the alleged attack, but officials said there could have been a "creative use" of a caustic agent.

CL17 is normal chlorine for swimming pools or industrial purposes. It is rated as Level 2 under the chemical weapons convention, which means it is dual purpose - it can be used as a weapon as well as for industrial or domestic purposes. Level 1 agents are chemicals whose sole use is as weapons, such as the nerve agents sarin or tabun.

There has been extensive experimentation by insurgents in Iraq in the use of chlorine, which is harmful when mixed with water to form hydrochloric acid. It vapourises quickly, meaning that in a big explosion it will evaporate; in a small blast - for instance, one delivered by a home-made rocket - it will turn into airborne droplets before dispersing quickly.

So it is likely only to produce limited casualties. In this case there were only 26 fatalities, far fewer than would be expected from a full chemical weapon attack. In short, it is easily improvised into a chemical device but not one that would be used by an army seeking mass-casualty effects.

Tellingly, just to the east of Aleppo, there is a rather nondescript factory whose purpose is to produce chlorine.

All claims by all sides in war need to be checked against available evidence. But what is clear in this case is that the Syrian claims do tally with some key agreed facts: the small number of casualties; proven availability of the chemical in the area; relatively low casualties; and a complaint taken seriously and acted upon by the UN with uncharacteristic speed.

Mr Ban said the UN would insist on "unfettered access" to the area under investigation. Allegations of chemical weapons usage are of course one of the most potent in the battle of claims and counter-claims in the conflict.

A government source confirmed that blood and soil samples had been collected and had been sent to the UN already. The UN has also been sent the phone numbers of the doctors involved.

Syria is believed to possess one of the largest stockpiles of chemical weapons in the world, allegedly holding supplies of sarin, mustard and VX gases, all banned under international law. Damascus denies the claims.

There have been repeated reports that Syria was moving chemical weapons as it lost control of swaths of the country to the rebels. As the civil war rages, one of the West's greatest fears is that these stockpiles could fall into the hands of Islamic extremists.

Alex Thomson is Chief Correspondent, Channel 4 News.