CAIRO: Arab League chief Ahmed Aboul Gheit said on Wednesday that a suspected chemical weapons attack on a rebel-held town in Syria that killed 72 people was "a major crime."

"Targeting and killing civilians with these prohibited methods is considered a major crime and a barbaric act," Aboul Gheit said.

"Whoever carried it out will not escape from justice, and must be punished by the international community according to international law and international humanitarian law," the Arab League chief said, without specifying who he held responsible.

The Syrian Observatory for Human Rights said Tuesday's air strike on the rebel-held town of Khan Sheikhun in Idlib province was likely carried out by government warplanes, a charge the regime denied.

Britain and the United States have pointed the finger at President Bashar al-Assad's government for the attack.

But Russia, which holds a veto in the UN Security Council defended its Syrian ally saying that the "toxic substances" which caused the deaths were in a "terrorist warehouse" on the ground which had been hit by the government air strike.

The Arab League suspended Syria's membership at the end of 2011 following months of brutal repression of anti-government demonstrations and an opposition movement supported by Gulf monarchies.