Members of an Al-Qaeda-linked militant group beheaded a pro-government militiaman in the latest clash in the troubled southern Philippines on Saturday, a military statement said.
Two members of the militant Abu Sayyaf group were also killed in the fighting against soldiers and pro-government volunteers in the strife-torn southern island of Basilan, the statement said.
The troops were guarding a town's water system following a series of extortion demands by Abu Sayyaf when they were attacked by about 20 gunmen.
"A fire fight ensued for five minutes (and) resulted in the death of (one civilian auxiliary) who was eventually beheaded," the report said.
Two Abu Sayyaf members were also killed in the fighting, the military said, adding that troops were pursuing the extremists.
Abu Sayyaf, set up with seed funding from Al-Qaeda in the early 1990s, has been blamed for many of the deadliest militant attacks in the Philippines, including the 2004 firebombing of a ferry on Manila Bay that claimed more than 100 lives.
The group has been known to behead some of its hostages and mutilate slain opponents.
It has engaged in mass kidnappings and extortion to raise funds and has proved resilient despite the Philippine military receiving US training to hunt them down.
A key leader of the group posted video footage of himself and other gunmen last year pledging allegiance to Islamic State fighters in Syria and Iraq.