An Al-Qaeda front group operating in Syria has killed a rebel chief in a firefight in the coastal province of Latakia, a monitoring group said on Friday.

The killing comes amid soaring tensions between the mainstream rebel Free Syrian Army (FSA) and its supporters and groups affiliated to Al-Qaeda, mostly made up of non-Syrian fighters.

Better known as Abu Bassir al-Jeblawi, rebel chief Kamal Hamami was shot dead Thursday by the Islamic State of Iraq and Syria (ISIS), one of the main jihadist groups operating in Syria, said the Syrian Observatory for Human Rights.

He was killed when ISIS fighters tried to destroy an FSA checkpoint in the Jabal al-Turkman region, in the north of Latakia province.

"FSA rebels fired into the air, and subsequently, an ISIS fighter shot Abu Bassir dead and wounded two other fighters from his battalion," said the Observatory, which relies on a broad network of activists, doctors and lawyers for its reports.

Late last week, dozens of FSA fighters were killed in a battle against ISIS in the northwestern province of Idlib. The FSA battalion chief there was beheaded by ISIS, said the Observatory.

On Thursday, ISIS released another rebel chief after holding him for 25 days alongside nine other insurgents, the group added.

ISIS is accused of holding dozens of prisoners in Raqa, the only provincial capital to have fallen out of the control of President Bashar al-Assad's regime.

Anti-Assad activists living in rebel areas are increasingly turning their attention to creating anti-ISIS campaigns, as the group's abuses multiply.

In the early days of the Syrian uprising, when opponents of the Assad regime were desperate for assistance from any quarter, jihadist fighters were welcomed but a spate of abuses has fuelled a growing backlash.

There are two main Al-Qaeda linked factions, both with Iraqi origins -- the Al-Nusra Front, which has operational independence, and the Islamic State of Iraq and Syria (ISIS), a front for Al-Qaeda in Iraq.

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