Thirteen Muslim separatist rebels and eight government soldiers were killed Monday as Muslim guerrillas attacked an army outpost in the southern Philippines, violating a two-year-old ceasefire.
Three soldiers were also abducted and two are still missing as the guerrillas from the Moro Islamic Liberation Front (MILF) virtually overran the outpost in the town of Mamasapano in the southern island of Mindanao, military officials said.
It was not clear how the clashes would affect ongoing peace talks scheduled to resume early this year.
Two soldiers were also wounded in the attack that began late Sunday when some 100 MILF rebels, armed with mortars and rocket-propelled grenades, swooped on the outpost.
Colonel Franklin del Prado, spokesman of the Philippine Army's 6th Infantry Division in the area, said the slain soldiers all belonged to the battalion base attacked by the MILF.
Helicopter gunships and artillery fire were called in to blast the MILF positions as the fighting continued into Monday, del Prado added.
He said reports from the field indicated that at least 13 MILF rebels were killed in the counter-offensive.
Eight guerrillas were also wounded in the clash, said local army commander Lieutenant Colonel Romulo Ocfemia.
Del Prado said the attack at Mamasapano, some 60km south of Cotabato city, was mounted by forces of MILF commander Abdul Rahman Binago whose brother, Fides Binago, leader of the Abu Sofia bandit group, was killed last week.
The attack indicated there was an alliance between the Abu Sofia, which has been involved in kidnappings and robberies, and the MILF, which had signed a ceasefire with Manila in 2002, he said.
MILF spokesman Eid Kabalu confirmed that Binago's forces had attacked the outpost in apparent retaliation for his brother's death but stressed that this was not sanctioned by the highest MILF leadership.
Kabalu said the MILF leadership was trying to contact Binago to get him to pull out and that an international team of ceasefire monitors was being rushed to the area to keep the fighting from spreading.
Some 50 security officials from Brunei, Malaysia and Libya have been deployed to the southern Philippines as part of an international team to monitor the ceasefire between the MILF and the government.
A Malaysian team is proceeding to the site of the fighting along with a joint government-MILF monitoring group, Kabalu said.
Del Prado was unable to confirm if the monitoring team had arrived.
Brigadier General Alexander Yano, who is part of the government's committee on the ceasefire, said the military understood that this was not an official MILF action and expressed hope that the fighting would not spread.
"We will try to contain hostilities within the immediate vicinity to prevent spilling over to other areas," he said.
The military was pursuing the attackers, Yano said but stressed that "our operations are targeted against the groups responsible for the attack and not against the MILF."
He said a joint ceasefire monitoring committee of the government and the MILF, along with representatives of the international monitoring team would meet soon in the southern city of Davao to discuss the incident.
The 12,000-strong MILF has been waging a 26-year rebellion in the southern third of this largely-Christian archipelago.
Despite the signing of the ceasefire and the start of initial peace talks, sporadic clashes and military allegations that rebel commanders are sheltering members of the regional Jemaah Islamiyah terror network have strained the already fragile peace process.