Islamist rebels in Syria have taken over much of the key north-western town of Jisr al-Shughur, activists say.

It is the last major town under government control in Idlib province and correspondents say it could give them a route into the heartland of the ruling elite's power.

The Islamist forces, including the al-Qaeda-affiliated al-Nusra Front, began the assault on Thursday.

State media said there was still fierce fighting on Saturday.

Government aircraft had bombed "groups of terrorists" and destroyed dozens of military vehicles, the Syrian state-run Sana news agency said.

But activists from the London-based Syrian Observatory for Human Rights said government forces had fled, though clashes were continuing in some neighbourhoods.

The bodies of at least 60 pro-government fighters were lying in the streets, the observatory added.

Before the rise of Islamic State, the Nusra Front was seen as the strongest and most militant rebel force.

The city of Idlib was overrun by the rebel groups last month.

Since then, government forces have been trying to protect their supply route between Aleppo and Hama province on one side and Latakia on the other.

BBC World Service Middle East analyst Sebastian Usher says that if the rebels can drive the government completely out of Idlib province, they would open the way to Latakia.

The city is home to the core of the Alawite minority to which the family of Syrian President Bashar al-Assad belongs and is so far largely untouched by the war.

The town of Jisr al-Shughur has been under government control since the early stages of the conflict. In June 2011, large protests against the regime led to the deaths of 120 troops in circumstances disputed by the government and its opponents.