Syria's UN ambassador alleged Tuesday that an opposition group had used "chemical material" during an attack near the city of Idlib.
With international pressure mounting on President Bashar al-Assad over the two year-old conflict, ambassador Bashar Jaafari told reporters the incident was an attempt to make it look as though government forces had used chemical arms.
Jaafari said "terrorist groups" had got into the town of Salaqeb and "spread seemingly the contents of plastic bags containing a kind of powder which must be most probably a chemical material."
The ambassador said many people were affected by the "heinous and irresponsible act" that was an attempt to "implicate the Syrian government on a false basis."
The Syrian government is refusing to let UN experts into the country to investigate whether chemical weapons have been used in the conflict, in which more than 70,000 people have been killed.
The government wants any investigation limited to its allegations that the opposition used chemical arms near the city of Aleppo last month. The United Nations and western countries want other allegations investigated.
Jaafari demanded that the UN provide the government with details of information given by Britain and France to the United Nations about the possible use of chemical weapons by government forces.
"There cannot be, at any time, a mission of investigation moving freely on Syrian territory just on the basis of letters containing allegations," he said.