The Syrian government and the opposition have accused each other of using chemical weapons during the conflict, and denied using them themselves. Both are keenly aware that they will be rendered moral support and international aid if the other side is believed to have used weapons of mass destruction.

Being suspicious for a long time.

Some experts in the field of chemical weapons proliferation believe that Syria has stocks of this kind of deadly weapons.

On July 23, 2012, Syria's Foreign Ministry spokesman appeared to admit Syria had chemical weapons, but it would only ever use them against a foreign invasion. The government quickly distanced itself from the comment and shortly after the spokesman was dismissed.

The following month, US President Barack Obama said his government would regard any use of chemical weapons by Damascus as crossing a "red line".

On March 19th this year, the Syrian government publicly accused the opposition of utilizing chemical weapons for the first time, alleging that at least 25 people were killed and 130 others wounded on that day when armed men fired a rocket filled with chemical materials in Khan al-Asal, near Aleppo.

On March 20th, the Syrian government made a request to the UN Secretary General Ban Ki-moon, asking for an independent investigation team to be dispatched to Syria to investigate.

Ban Ki-moon announced the formation of a UN inspection team at the end of March. But differences between the Syria, Russia and Western governments on the authority of the team delayed the visit for months.

From May to June, the UK, France, and the US made a succession of claims that the Syrian government had used chemical weapons on a small scale.

But in less than one month, Russia's ambassador to the UN said Moscow has proof that rebels had been responsible for a sarin gas attack in the northern town of Khan al-Assal.

Last month Syria announced its troops had seized a weapons laboratory with a massive quantity of chemicals being made by rebels in the eastern outskirts of Damascus.

Finally on August 18th, a team of UN inspectors arrived in Damascus for a 14-day mission to investigate three sites of alleged chemical attacks.