"If the information concerning the use of chemical weapons is accurate, very definitely they were used by terrorist groups... who have shown they will not hold back from committing any crime," Foreign Minister Mohammad Javad Zarif was quoted as saying in his phone call with his Turkish counterpart Ahmet Davutoglu.

"With United Nations (chemical weapons) inspectors now in Damascus and the Syrian government’s troops’ great advances in driving back terrorist groups, why would it (Syrian government) commit such an act," he asked.

Zarif said Tehran "vigorously condemns any use of chemical weapons," while accusing the terrorist groups of having "every interest in aggravating and internationalizing the crisis."

Syria's main opposition group, the National Coalition, allegedly accused the government of "massacring" more than 1,300 people in chemical weapons attacks on Wednesday.

The accusation, which was strongly denied by Damascus, came as a team of UN inspectors was in Syria to probe previous allegations of chemical weapons strikes leveled against both sides during the 29-month conflict.

NJF/NJF