A jihadist group that has pledged allegiance to Al Qaeda has taken over swathes of Syria as western forces have focused their efforts on defeating Islamic State.

The al-Nusra Front have carved out their own territory in the region, raising fears a second jihadist mini-state could thwart any attempts to end the barbarity.

The hardline Islamist fighting group has been gaining control across Idlib province in northern Syria since November, driving out other rebel groups, including western-armed moderates.

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Gaining control: The al-Nusra Front have carved out their own territory in the region, marked above in pink, raising fears a second jihadist mini-state could thwart any attempts by western forces to end the barbarity

Syrian rebel activists and commanders have said that in the past week – as airstrikes have focused around IS strongholds in the region – the Nusra Front have begun to extend its control into the northern city of Aleppo.

Aleppo is seen as one of the last areas in northern Syria with a significant presence of moderate rebel groups.

Mazen Alhor, an opposition activist in the city, said: ‘Nusra are trying to do in Aleppo what they did in Idlib — they want to wipe out the (western-backed) Free Syrian Army.

‘They are starting to behave like ISIS — kidnapping, enforcing Islamic rules. They have a strategy, they want an Islamic state.’

Sami Mashaal, the head of the Shura Council for the Revolution in Aleppo, said that on Wednesday the Nusra Front began establishing checkpoints inside the city.

He said: ‘They are harassing people, trying to enforce Islamic rules — and civilians are getting angry about it.’

Violence: In the past week the Nusra Front have begun to extend its control into the northern city of Aleppo, pictured above after a clash between members of the Free Syrian Army and forces loyal to Assad last week

Conflict: The Nusra Front has turned against the Islamic State after it was previously allied to the extremist group that eventually morphed into ISIS. Above, ISIS militants pictured in Aleppo in 2013

The Nusra Front was established inside Syria in 2012 under Abu Muhammad al-Julani, a Syrian al-Qaeda commander, and was originally allied to the extremist group that eventually morphed into Islamic State.

The two groups turned against each other at the start of last year however, in a war that has cost thousands of lives.

The emergence of a new mini-state alongside the IS ‘caliphate’ could jeopardise western plans to train thousands of moderate rebel groups to fight Islamic State.

A few weeks ago Britain announced plans to help train the moderate groups alongside other coalition partners in countries bordering the region.