"Al-Nusra Front and its allies have captured all of Idlib," the Britain-based Observatory announced on Saturday, after five days of intense fighting in the western Syrian city.

"Thanks be to God, the city of Idlib has been liberated," the jihadist group, which is Syria's official al Qaeda affiliate, wrote on one of its Twitter accounts.

The group also posted photos showing its fighters in front of Idlib's city council, a local prison and a police station in the city.

The city's fall comes after fighting between a coalition of Al-Nusra and various Islamist opposition allies and the regime.

Second capital to fall

More than 130 people have been killed in the fighting, according to the Observatory.

The first provincial capital to fall from regime control was Raqa, in northern Syria. It was lost in March 2013 to rebels who were subsequently pushed out by the Islamic State group. The city has subsequently become the self-proclaimed group's headquarters.

glb/sb (Reuters, AFP, dpa)