Moderate Islamist rebels besieged the headquarters of an al-Qaeda—linked group on Monday in eastern Syria as fighting between rival rebel groups spread across the country.

Rebels besieged the office of the Islamic State in Iraq and the Levant (ISIL) in Raqqa, said the Syrian Observatory for Human Rights, a Britain—based pro—opposition watchdog.

They also released 50 people jailed by the militant group in another building.

The fighting pitting secular and moderate Islamist opponents of Syrian President Bashar al—Assad against al—Qaeda—affiliated militants began in northern Syria Friday, killing dozens of fighters.

The Syrian conflict, which has lasted for nearly three years, has resulted in several radical groups imposing strict Islamic rules in areas under their control, triggering fears that the country is turning into a hotbed of Islamist militancy.

Earlier Monday, a coalition of Syrian opposition groups said it had re—elected Ahmad al—Jarba as its leader in a vote in Istanbul.

Al—Jarba, who has led the Syrian National Coalition since July, beat his only rival for the post of president, Riad Hijab, a former Syrian premier who defected in 2012.

The coalition also elected three vice presidents during a general assembly at its base in the Turkish city.

Al—Jarba’s re—election came two weeks before a peace conference in Geneva, dubbed Geneva II, due to take place January 22.

The coalition has said it will attend the meeting but will not accept any future role for al—Assad in Syria.

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