Israeli Defence Minister Moshe Yaalon said on Wednesday that the Syrian government had used chemical weapons, backing opposition claims of multiple deadly strikes around Damascus.

"In Syria, the regime has used chemical weapons and it's not the first time," Yaalon told Israeli defence correspondents.

"It's a life and death struggle between a regime based on the Alawite minority and a disparate opposition composed of Sunni Muslims, some Muslim Brotherhood members, others linked to Al-Qaeda.

"We don't see any end to the fighting -- even the fall of (President Bashar) al-Assad won't bring it to a halt, there will a bloody settling of accounts over a long period," the minister said.

"We could see the implosion of Syria with the Alawites controlling the western part -- the coastal region and a corridor to Damascus -- and the Kurds and Sunnis controlling the east and north."

The head of research at Israeli military intelligence, Brigadier General Itai Brun, already said in April that he believed the Syrian regime had made use of its chemical weapons stockpiles against the rebels.

Syria's main opposition group accused the government of "massacring" more than 1,300 people in chemical weapons attacks near Damascus on Wednesday, saying many of the victims choked to death.

The accusation came as a team of UN inspectors was in Syria to probe previous allegations of chemical weapons strikes levelled against both sides during the 29-month conflict.

Western governments demanded immediate access for the inspectors to investigate the new allegations. Russia, a longstanding ally of the Damascus regime, echoed the call for an inquiry but said it suspected a "provocation" by the opposition and its foreign backers.