Saudi Arabia's Foreign Minister Prince Saud Al-Faisal on Tuesday said the "grave news" that President Bashar Al-Assad's forces had carried out two poison gas attacks last week was a challenge to "international will".

Rebels and the Syrian government have blamed each other for the alleged poison gas attacks on Friday and Saturday on rebel-held Kfar Zeita village in the central province of Hama. Both sides said chlorine gas had been used.

"These continuous violations by the Damascus regime require the international community to take firm action against the continuous defiance of international, Arab and Islamic will," Prince Saud said at a news conference in Riyadh.

The reported gas attacks posed a clear challenge to the Security Council decision to dismantle Assad's chemical arsenal, he said.

Saudi Arabia is a leading backer of rebels fighting against Assad, who is a close ally of the kingdom's main rival Shi'ite power Iran. It has supplied rebels with training, weapons and cash and worked to mobilise international support for them.

Asked about the possibility of supplying anti-aircraft weapons to the rebels, Prince Saud said that it was necessary to change the balance of military power on the ground in Syria but did not give further details.

"The only way the regime would listen to calls for peace is if he (Assad) is forced to agree that we cannot reach a military solution for his desire to quell the revolution," he said.

Chlorine gas, a deadly agent widely used in World War I, has industrial uses and is not on a list of chemical weapons that Assad declared to the global chemical weapons watchdog last year for destruction.

"Chlorine was not part of the declared stockpile but chlorine is a chemical weapon under the chemical weapon convention," said Hamish de Bretton-Gordon, CEO of SecureBio, a UK-based consultancy firm.

De Bretton-Gordon said that while chlorine gas was readily available in Syria, the attacks consisted of chlorine containers being dropped from helicopters.

"As far as I am aware, the opposition does not have helicopters," he said.  - Reuters