Syrian militants sent reinforcements to fight the Islamic State group in the northern province of Aleppo, where rival factions battled Tuesday near the Turkish border, activists said.

The Britain-based Syrian Observatory for Human Rights and Abu al-Hassan Marea, who is currently in Turkey near the Syrian border, said that the battles raged on the northern edge of Aleppo province.

Islamic State fighters captured four villages and a town from Al Qaeda's branch in Syria, the Nusra Front, and its allies over the past days in battles in the area.

On Tuesday, the pro-Islamic State Aamaq News Agency released a video showing fighters with the group as they captured the northern village of Umm al-Qura. The video showed the fighters marching in fields near the village, as well others shooting from what appeared to be the roof of a building.

"Thank God, with His help the brothers of the Islamic caliphate advanced at several northern countryside villages," an unidentified Islamic State fighter said in the video. "God has made it easy for us to get hold of their necks and we were able to kill 35 and what is coming is worse for them than this."

The video appeared genuine and corresponded to other Associated Press reporting of the events.

Marea said the reinforcements are being sent from other parts of Aleppo province, as well as the nearby region of Idlib, where rebels recently captured wide areas from government forces, including the provincial capital.

The fighting came a day after U.S. State Department spokeswoman Marie Harf said authorities heard reports that forces loyal to Syrian President Bashar Assad launched airstrikes supporting the Islamic State group's advance.

"Beyond that, we have long seen that the regime avoids ISIL lines, in complete contradiction to the regime's claims publicly to be fighting ISIL," Harf said, using an alternate acronym for the group. "As we have long said, Bashar Assad has lost legitimacy long ago and will never be an effective counterterrorism partner, despite what he might say publicly."