Day-long clashes between Al Qaida-linked Muslim militants and Philippine troops on a southern island killed 12 army soldiers and four rebels, the military said Friday (local time).
It was one of the bloodiest days in recent weeks in the volatile south.
The violence started early Thursday when soldiers attacked an Abu Sayyaf encampment on Basilan Island's Sumisip township. The battle left eight government troops and four rebels dead, Army Maj. Gen. Ricardo Rainier Cruz said.
The army sent more troops and sporadic fighting continued until the afternoon.
Later in the day, the Abu Sayyaf militants fired at an army outpost in the same township, said Capt. Albert Caber, a military spokesman. They then separately ambushed two groups of troops sent to back up the forces there.
No one was killed at the outpost, but four reinforcement troops were killed en route to the area, Caber said.
At least three soldiers and two rebels also were wounded in Thursday's clashes.
Officials said the militants belonged to the same group that ambushed a truckload of rubber plantation workers in Sumisip two weeks ago. Five farm workers and one government militiaman were killed in that attack, while 22 others were wounded.
On Wednesday, the same group of militants attacked a military detachment providing security for the rubber planters' cooperative, but no soldier was killed or hurt, officials added.
Violence in the southern Philippines continues despite efforts by U.S.-trained Philippine forces to put an end to decades of bombings and ransom kidnappings by Muslim extremists in the predominantly Christian nation.
The Abu Sayyaf has received funding and training from al-Qaida and is on a U.S. list of terrorist organizations.
Philippine offensives have weakened the militants, but they remain a threat. They are holding several foreign hostages, apparently to raise ransom money to buy food and weapons.