|At least 25 soldiers were killed in the clash, which followed a rebel ambush, the Philippine military said [Reuters]
At least 25 people have been killed during fighting between Philippine special forces and rebels in the country's south.
The Philippine army said it was searching for several missing soldiers after the clashes, the worst in the area for three years. Both soldiers and rebels from the Moro Islamic Liberation Front (MILF) were among those killed, and several more soldiers were reported injured.
The violence has thrown an already shaky ceasefire into further jeopardy.
The clash erupted early on Tuesday morning, after a Philippine army platoon encountered the rebels near Barka town on the island province of Basilan, according to an army spokesman.
The soldiers were checking reports of a kidnapping incident involving Abu Sayyaf fighters when the rebels stormed in, said Lieutenant Colonel Randolph Cabangbang.
He said the troops were attacked by a MILF unit led by Dan Laksaw Ansawi, a rebel leader who escaped from a Basilan jail in 2009. Several missing soldiers were believed to be held by the MILF, he said.
"We are currently co-ordinating with the ad-hoc joint action group and the committee on cessation and hostilities to contact the MILF, to verify the report," he added.
Von al-Haq, a spokesman for the MILF, was unable to confirm on Tuesday that the group was holding the soldiers.
"We have yet to receive information from our forces on the ground that they are holding the soldiers," he told the AFP news agency.
He added that if the troops were being held, they would be released.
The MILF insists that the government were the aggressors in the latest clash, and that its fighters were now on alert.
Two helicopter gunships and two OV-10 aircraft were deployed to quell the fighting and rescue the wounded, the military said.
An undetermined number of rebels have been wounded by air strikes and ground bombardment in the latest clashes.
"It was the bloodiest encounter between the military and armed Muslim guerillas in the last few years," reported Al Jazeera's Marga Ortigas from North Cotabato in the Philippines.
The 12,000-strong MILF has been negotiating with the government to end more than four decades of conflict that has killed at least 120,000 people and displaced two million.
Talks in Malaysia have been stalled since August, when rebel leaders rejected a deal that would allow for a certain degree of autonomy. They demanded a sub-state be created.
The Philippines' south is resource-rich, but the conflict has also stunted economic growth.
A truce was signed in 2003, but the ceasefire is frequently broken by sporadic violence.