MANILA, Philippines (AP) — After years of fighting the government from hidden jungle bases in the southern Philippines, an Al-Qaida-linked militant group is facing a new adversary: fellow Muslim insurgents who can match their guerrilla battle tactics and are eager to regain their lost stature by fighting the widely condemned terrorist group.

The emerging enmity between the Abu Sayyaf militants and the Moro rebels could bolster a decade-long campaign by the Philippines and Western countries to isolate the al-Qaida offshoot Abu Sayyaf, which remains one of the most dangerous groups in Southeast Asia.

In their first known major clash, Abu Sayyaf gunmen battled rebels from the larger Moro National Liberation Front in fighting early this week, leaving at least 22 combatants dead in the mountainous jungles on southern Jolo Island. A Moro rebel was beheaded — Abu Sayyaf’s signature act.

Bonded by blood ties and war, the two armed groups had co-existed for years on Jolo in a predominantly Muslim region, where abject poverty, guns and weak law enforcement have combined in an explosive mix to fuel their rebellions and pockets of lawlessness.

The trouble began after the Moro rebels — seeking to regain their former dominance in the region — tried to arrange the release of several hostages held by the Abu Sayyaf, including a prominent Jordanian TV journalist and two European tourists. When the Abu Sayyaf commanders refused to free the hostages, Moro rebels launched an attack.

The Moro rebels are now trying to rescue the captives and end the Abu Sayyaf’s reign, Moro commander Khabier Malik told The Associated Press.

“We breath the same air, speak the same language and live and fight in the same jungle,” he said by telephone. “We’re a bigger force and we cannot allow this small group to reign with this brutality.”

For years, a shadowy alliance is believed to have existed between the groups. While the Moro rebels signed a limited peace deal with the government years ago, some Moro commanders are suspected of giving sanctuary to Abu Sayyaf men and carrying out kidnappings for ransom with them.

“Collusion between the Abu Sayyaf Group and MNLF members — many of whom are relatives — on Jolo is a major reason why large swaths of the island have been essentially ungovernable for years,” said Bryony Lau of the Brussels-based International Crisis Group think tank. The government “should consider whether the recent clash has shifted relations between them in a way that could make it easier to isolate senior figures of the Abu Sayyaf Group.”

But the rift offers no easy answers for the Philippines. Weaning the Moro rebels from hardened militants would mean a true government alliance with the rebels, some of whom are suspected of involvement in attacks on civilians and government forces.

Walking a tightrope amid the clashes, President Benigno Aquino III said the Moro offensive was not sanctioned by his government. But government officials also are not trying to stop the fighting, presumably hoping each group weakens the other. Police and soldiers have simply set up checkpoints to seal off the area around the fighting, trying to keep it from spilling into other rural areas.

Sulu provincial Governor Abdusakur Tan said he would allow the Moro attacks to continue, at least for now.

“They’re cleaning their ranks. These kidnappers are either their former members or one of their own,” Tan said.

The Moro National Liberation Front spearheaded an underground movement in the early 1970s for a separatist Islamic state. But it dropped its secessionist goal when it accepted limited autonomy for minority Muslims in the predominantly Roman Catholic nation’s south, prompting key guerrillas to break away, including a Libyan-educated radical, who established the Abu Sayyaf.

Another major guerrilla bloc broke off from the original Moro group and formed the Moro Islamic Liberation Front, which has emerged as the country’s largest Muslim rebel group.

The Moro rebels were not required to disarm under the landmark 1996 peace deal, allowing fighters to settle to their Jolo communities with their weapons. The accord also lacked a provision to formally enlist the rebels in hunting down criminals and terrorists straying into their strongholds, an oversight that may have helped foster collusion years later between the Moro rebels and the Abu Sayyaf.

Philippine officials forged such a pact in peace talks with the Moro Islamic Liberation Front with impressive results. Hunted by U.S.-backed Filipino troops in 2005, Abu Sayyaf chieftain Khadaffy Janjalani and other militants sought refuge in a stronghold Moro Islamic Liberation Front, which turned them away. Janjalani, then among the most-wanted terrorist suspects in Southeast Asia, was killed by troops the following year on Jolo.

The Abu Sayyaf — “Bearer of the Sword” in Arabic — was founded with funds and training believed to come from a collection of Asian and Middle Eastern radical groups, including al-Qaida. It came to U.S. attention in 2001 when it kidnapped three Americans, one of whom was beheaded, along with dozens of Filipinos and openly swore allegiance to Osama bin Laden’s movement.

The kidnappings prompted Washington to deploy hundreds of troops in the south in 2002 to train Philippine forces and share intelligence, helping the military capture or kill most of the Abu Sayyaf’s top commanders. Now without a central leader, the group has less than 400 armed fighters, who the military says are constantly on the run from U.S.-backed local offensives.

Philippine security officials attribute the Abu Sayyaf’s resilience to the difficulty of hunting down small pockets of fighters by soldiers unfamiliar with the vast mountainous jungles of Jolo and outlying islands.