Syrian army behind chemical attack: HRW

Human Rights Watch says the Syrian army was most likely to blame for the chemical weapons attack that killed hundreds last month.

Syrian government forces were most likely to blame for the deadly chemical weapons attack last month which left hundreds dead, Human Rights Watch says.

A 22-page report issued by the US rights watchdog concluded that available evidence "strongly suggests" that President Bashar al-Assad's military carried out the strike.

Human Rights Watch issued its findings after analysing witness accounts of the rocket attacks in Ghouta on August 21, information on the likely source of the attacks, physical debris from weapons used, and the victims' medical symptoms.

"Rocket debris and symptoms of the victims from the August 21 attacks on Ghouta provide telltale evidence about the weapons systems used," said HRW emergencies director Peter Bouckaert on Tuesday.

"This evidence strongly suggests that Syrian government troops launched rockets carrying chemical warheads into the Damascus suburbs that terrible morning."

The rights group said the type of rockets and launchers used in the attack were known to "be only in the possession of and used by" the Syrian armed forces.

The United States says more than 1400 people, including 400 children, were gassed in the attack, which has prompted the threat of punitive military strikes by President Barack Obama.

Other outside estimates have set a lower but still high death toll.

Western states and the Arab League have condemned the alleged barrage as a war crime and blamed it on Assad's regime, which has denied the charges.

Human Rights Watch said the nerve agent sarin was most likely used in the attack.

The rights group also said two kinds of rockets appeared to have been used -- a 330mm rocket with a warhead designed to carry a large payload of liquid chemical agent, and a smaller 140mm rocket capable of carrying a warhead packed with 2.2kg of sarin.

Human Rights Watch described the attack as the first major use of chemical weapons since the Iraqi government gassed Iraqi Kurdish civilians in Halabja 25 years ago.

"The increasingly evident use of chemical weapons in Syria's terrible conflict should refocus the international debate on deterring the use of such weapons and more broadly protecting Syria's civilian population," Bouckhaert said.