Mustard gas used in Syria

Mustard gas was used during summer fighting in Syria but it was not clear by whom, the global chemical weapons watchdog said Thursday, while jihadists seized a key town from regime forces.

The deadly gas was used in the flashpoint town of Marea in the northern province of Aleppo on August 21, a source from the Organisation for the Prohibition of Chemical Weapons (OPCW) told AFP.

"We have determined the facts, but we have not determined who was responsible," the source said.

Meanwhile, France has announced that it will deploy its only aircraft carrier to boost its efforts in the fight against IS.

In a statement by the French presidency following a meeting of its defence cabinet, the government said the Charles de Gaulle warship would be sent to the eastern Mediterranean for operations against IS in both Syria and Iraq, reports Independent.

"The deployment of the battle group alongside the Charles de Gaulle aircraft carrier has been decided to participate in operations against Daesch and its affiliate groups," the statement said after a defence cabinet meeting, referring to the Arabic acronym for Islamic State.

The Syrian Observatory for Human Rights said yesterday air strikes by Russian warplanes on the Islamic State-held Syrian city of Raqqa killed 42 people earlier this week, including 27 civilians.

Fifteen Islamic State fighters made up the remainder of the death toll, the Britain-based Observatory said, after a series of strikes on Tuesday that hit the group's Syrian stronghold, reports Reuters.

Allegations that jihadist militants have been using chemical arms have been increasing in recent months in both Iraq and Syria.

Doctors Without Borders (MSF) said it had treated four civilians from one family. Patients at an MSF hospital in Aleppo said they saw a "yellow gas" when a mortar round hit their house.

Syrian rebels and aid groups said that at the end of August dozens of people were affected by a chemical attack on Marea, where moderate opposition rebels and militants from the Islamic State (IS) group were battling.