BEIRUT (AP) — Syria's ragtag rebel groups and insurgents trying to oust President Bashar Assad have turned their guns on each other in some of the worst infighting yet, with al-Qaida-linked fighters battling other factions in a split between supporters and opponents of the Russian-led push for a new peace process for the war-torn country.

The clashes — mainly in opposition-held areas in northern Syria — have led to the formation of two new coalitions but have also raised the specter of more fractures among rebel factions, already struggling to recover from their December loss of the eastern half of the city of Aleppo to Assad's forces.

At the root of the infighting is a call that came at the end of the peace talks last month in the Kazakh capital of Astana. Russia, Turkey and Iran — sponsors of the gathering — urged Syria's rebels to dissociate themselves from al-Qaida's affiliate in Syria, now known as the Fatah al-Sham Front.

The Astana meeting was designed to pave the way for political talks to be held in Geneva in late February but it also marked a new push in efforts to resolve Syria's conflict, with Russia and Iran, Assad's main supporters, and Turkey, the rebels' chief backer, pledging to put their influence behind the truce. The United States, busy with the presidential transition, played no significant role in Astana.

The Fatah al-Sham Front, previously called the Nusra Front, has been excluded from all negotiations and cease-fires, along with the Islamic State group — both considered by the international community to be terrorist organizations.

For the rebels, however, the exclusion of al-Qaida's affiliate is a sore point as many groups have close links with it on the ground, perceiving it to be the most powerful force against Assad's army and allied militiamen.

Fatah al-Sham signaled its determination to fight back — even as the rebels were still sitting at the table in Astana.

On Jan. 23, Fatah al-Sham fighters surrounded the offices in Idlib province belonging to one of the rebel groups that had sent representatives to Astana, the U.S.-backed Jaish al-Mujadeen, and hours later, forced its fighters to surrender.

"Al-Qaida has been waging a campaign to sideline and ultimately eliminate moderate opposition groups since it entered Syria," said Jennifer Cafarella of the Washington-based Institute for the Study of War.

Al-Qaida's affiliate in Syria, which lost many senior leaders in targeted assassinations in recent months, had accused Jaish al-Mujahdeen of giving the U.S.-led coalition intelligence on the location of their commanders and top figures.

The Idlib attack was not the first assault by al-Qaida's fighters — the militants have on several occasions since late 2014 defeated moderate rebel factions, including those backed by the United States. But the Jan. 23 fighting quickly escalated to include other groups, leading to fierce clashes between Fatah al-Sham and more moderate factions.

To seek protection from Fatah al-Sham, many small groups turned to the ultraconservative Ahrar al-Sham, one of Syria's most powerful insurgent groups and a former ally of al-Qaida. This in turn led to the formation of two broad coalitions in northern Syria, effectively pitting Fatah al-Sham against Ahrar al-Sham.

Ahrar al-Sham did not take part in the Astana talks but groups that joined it later did attend.

A Fatah al-Sham member, who has been frequently contacted by The Associated Press over the situation in northern Syria, said on Tuesday that since the latest round of fighting began last month, he had left to join Ahrar al-Sham.

"They wanted to wipe out Ahrar al-Sham but they were not able to," said the member, referring to Fatah al-Sham. Speaking on condition of anonymity for fear of reprisals, he added that he did not take part in the Idlib clashes between Ahrar al-Sham and Fatah al-Sham.

Most of the fighting that followed eventually prompted the al-Qaida affiliate to issue a statement calling for unity among all insurgent groups under a "unified political and military command."

The rebel infighting and reshuffling of alliances — if it continues — could facilitate a break between Fatah al-Sham and moderate groups, making it easier for the international community to single out the al-Qaida affiliate for attack.

However, for Cafarella, the Idlib developments do not reflect the "sorting" of al-Qaida from other factions as some analysts have argued. Rather, she said it's "the next step ... in al-Qaida's campaign to transform the opposition in its own image."

Rami Abdurrahman who heads the Britain-based Syrian Observatory for Human Rights said that his activist network, which has tracked the six years of Syria's civil war, registered only 14 dead on both sides but that he suspects the factions are keeping secret the real number of their fatalities.

One of the two new coalitions that emerged is The Levant Liberation Committee, under Abu Jaber Hashem, a hard-liner and former Ahrar al-Sham member. It includes Fatah al-Sham, Nour el-Din el-Zinki, The Brigade of Righteous, Jaish al-Sunnah and Ansar al-Deen Front.

The other coalition is made up groups that have melted into Ahrar al-Sham, including Suqour al-Sham, Jaish al-Islam's Idlib branch, the Levantine Front, the al-Farouq Brigade and the Al-Sham rebels.

Ahrar al-Sham's top commander, Ali al-Omar, accused Fatah al-Sham in a statement posted on YouTube recently of "oppressing" the more moderate rebels and rejected the al-Qaida affiliate's call for unity.

Syria's armed opposition has struggled for years to unify behind a leadership, political or military. Efforts were always short-lived and often self-destructed. The Syrian government has labeled all armed opposition groups "terrorists" and says they are backed by foreign enemies, particularly with the influx of foreign fighters to an increasingly complex battlefield.

Asaad Kanjo, an opposition activist originally from Idlib province now living in Britain, said the rebel infighting is mostly taking place in Idlib province but also in small parts of Aleppo province.

He said Fatah al-Sham and its allies have been sending fighters to the border town of Sarmada, which is an Ahrar al-Sham stronghold, and a nearby border crossing point to Turkey — in preparation for what may be their next showdown.

"We are yet to see more fierce battles between them," Kanjo said.