Eighteen soldiers and five militants died in the worst violence this year in the southern Philippines, following a military offensive against the extremist Abu Sayyaf group.
The military said on April 10 that the fighting took place the previous day in the Tipo-Tipo town of Basilan province, 900 kilometers south of Manila.
The clashes took place after the passing of an April 8 deadline by Abu Sayyaf, who had threatened to behead some of their foreign hostages.
There have been no reports on the fate of the hostages since the passing of the deadline.
The soldiers were on their way to attack an Abu Sayyaf hideout when they were ambushed.
The military has been stepping up its offensive against the Abu Sayyaf group, which has blamed for some of the deadliest terrorist attacks in the Philippines, as well as high-profile kidnappings for ransom involving foreign hostages.