Syrian activist groups are reporting another chemical attack in the northwestern province of Idlib.

Several Idlib-based groups say government helicopters dropped at least two barrel bombs containing chlorine on the town of Saraqeb, triggering cases of suffocation.

The Syrian Network for Human Rights, which is based outside the country, has tweeted that 12 people were "suffocating."

The reports could not be independently verified.

The head of Syria's main opposition group in exile says it received the reports Wednesday during an informal meeting with the U.N. Security Council behind closed doors.

Khaled Khoja with the Syrian National Coalition urged the council to act on its resolutions, including one that threatens action against the use of chemical weapons.

Activists have reported several attacks since the resolution was adopted last month.