Four navy commandos have been killed in a gun fight with suspected Islamist militants in the southern Philippines, military officials have said.
Troops have been fighting militants in the region for several months
At least six militants died in the clash, which took place on Lanhil island, north-east of restive Basilan.
The Philippine military recently stepped up its offensive against militants in the south of the country.
Both sides have suffered heavy death tolls in fierce clashes on the islands of Basilan and neighbouring Jolo.
In August, 26 soldiers and around 30 militants were killed a clash in Jolo. A month before that, 14 marines were killed in Basilan. Ten of them were beheaded.
Military spokesman Maj Eugene Batara said that troops had been despatched to the small island of Lanhil in response to reports from residents that militants were present.
A 35-minute gun fight erupted just after midnight, he said.
Two other naval personnel were injured in the fighting but were in a stable condition, he said.
He blamed the violence on rebels from the Abu Sayyaf group, which the US has listed as a terrorist organisation and says has links to al-Qaeda.
Militants from other organisations, including regional group Jemaah Islamiah, are also thought to be in the area.
In August, Philippine President Gloria Arroyo authorised a new military offensive against the militants and sent 1,000 troops to reinforce the 4,000 already deployed in the region.