An extremist group embroiled in infighting with one of the largest Syrian rebel groups has pledged allegiance to al-Qaida-linked militants in Syria.

The extremist group Jund al-Aqsa has been battling the powerful Ahrar al-Sham group in northern Syria for days, after the latter accused it of ambushing its leaders. Scores of factions rallied behind Ahrar al-Sham accusing Jund al-Aqsa of serving the extremist Islamic State militants, who are at odds with all Syrian insurgents, including the al-Qaida-linked Fatah al-Sham Front.

On Sunday, Fatah al-Sham Front announced Jund al-Aqsa would join its ranks. The declaration is expected to put an immediate end to the infighting.

It has also drawn criticism from other rebel groups, however, who see the move as divisive, providing cover for an extremist group.