Several Syrian opposition groups united on Thursday (January 26th) against the war-torn country's former al-Qaeda affiliate, as clashes raged for a third day between anti-regime forces, AFP reported.

Five opposition groups joined the Ahrar al-Sham group to fight against Al-Nusra Front (ANF), which changed its name to Fatah al-Sham Front last year after allegedly breaking ties with al-Qaeda.

The clashes erupted earlier this week as the opposition attended peace talks in the Kazakh capital Astana, building on a fragile nationwide ceasefire.

ANF, which is excluded from the ceasefire and did not attend the Astana talks, much like the "Islamic State of Iraq and Syria" (ISIL), has accused opposition groups of having brokered a deal to fight and destroy its organisation.

On Tuesday, ANF attacked a base belonging to the Jaish al-Mujahideen faction , sparking fighting between it and opposition groups in the northern provinces of Idlib and neighbouring Aleppo.

"In the past hours a series of aggressions have targeted our blessed revolution, leading to total confrontation," Ahrar al-Sham said in a statement on Thursday.

This caused five opposition groups including Jaish al-Mujahideen and Suqur al-Sham to ask to become part of Ahrar al-Sham, it said.

"All attacks against members of the movement or its bases will be considered as a declaration of war," the statement warned.