BEIRUT, Lebanon — Deadly clashes were reported Friday in northern Syria between Sunni Islamist jihadists linked to Al Qaeda and insurgents in other alliances, punctuating a growing schism within the armed Syrian opposition over the power exerted by its religiously radicalized members, many of them from other countries.

Antigovernment activists in the Aleppo area said that fighting had broken out near the Idlib Province town of Atareb, west of Aleppo, pitting members of the Islamic State of Iraq and Syria, or ISIS, a powerful Qaeda affiliate that includes foreign fighters, against an array of seven homegrown Syrian rebel groups. The rebels call themselves the Mujahedeen Army, and they resent what they see as the affiliate’s hijacking of their struggle, now nearly three years old, to depose President Bashar al-Assad.

The Mujahedeen Army also issued a statement in Arabic on Facebook essentially announcing that it now considered the Islamic State of Iraq and Syria an enemy.

“We, the Mujahedeen Army, declare that we will defend ourselves, our honor, properties and land and we declare the fight against the ISIS organization, the unjust to God’s law, until it dissolves its formation and its members join other military formations or abandon their arms and leave Syria,” the statement read.