Syrian activists say Al Qaeda fighters are amassing in a Syrian border town in what appears to be an attempt to seize a nearby Turkish border crossing from Syrian rebels.

Assad Kanjo said Monday that Nusra Front fighters have been gathering in the town of Sarmada in the northern Idlib province, some 4 miles from Bab al-Hawa, an important Turkish border crossing.

If Nusra Front fighters seize the crossing, it would block an important supply line for Western-backed rebels.

Kanjo said Nusra fighters have been gathering there for days, as part of their weeklong attack on Idlib province, where they have wrested towns and villages from rebels, mostly belonging to the Western-backed Syrian Revolutionary Front.

The Britain-based Syrian Observatory for Human Rights also confirmed the details.