Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on 28 March.

By taking Idlib, the capital of a north-western province of the same name, hardline Islamist insurgents now control a second province after Raqqa, the stronghold of the Islamic State (IS) which has been the target of US-led air strikes.

Sunni Islamist groups have formed an alliance which includes Nusra, the hardline Ahrar al-Sham movement and Jund al-Aqsa, but not Islamic State, their rival.

They launched the offensive to capture Idlib city on 24 March.

Video uploaded to social media sites appeared to show prisoners running free from an Idlib jail while rebels said other prisoners were shot dead before government forces escaped.

Idlib, a city whose population has been swollen by hundreds of thousands of displaced people from other parts of Syria, is close to the strategic highway linking Damascus to Aleppo and to the coastal province of Latakia, a stronghold of President Bashar al-Assad.

Many civilians are now fleeing the city with militants setting up checkpoints on the outskirts to check people's IDs as they leave town.

The Islamist alliance which says it has taken control of Idlib calls its operation Army of Fatah, a reference to the conquests that spread Islam across the Middle East from the seventh century.