MANILA (REUTERS) - Philippine security forces killed about 36 ISIS-linked militants in a three-day air and ground assault on a southern island, and captured the rebels' base, an army general said on Monday (April 24).

Security forces in the mostly Christian Philippines have battled Muslim separatist rebels for decades. In recent years, peace efforts have led to a reduction in clashes with main groups but small, violent factions have stepped up attacks.

The latest clash, on the main southern island of Mindanao, erupted on Friday when soldiers stumbled upon a well-fortified base of a faction known as Maute, guarded by about 150 fighters.

"We captured their main base," Brigadier-General Roland Bautista, an army division commander, told reporters.

Government forces used artillery and air strikes to hit the militant base and inflict the casualties, he said. Only three government soldiers were wounded, he said.

A spokesman for the militant faction was not available for comment and Reuters was not able to independently verify the military's account.

Bautista said surviving militants had split up into small groups and fled.

The faction, which has pledged allegiance to the Islamic State in Iraq and Syria (ISIS), has been accused of bomb attacks including one in President Rodrigo Duterte's hometown of Davao City in September that killed 14 people.

Bautista said the army suspected militants from neighbouring Indonesia and Malaysia might have been with the band and an Indonesian passport had been recovered, along with arms and explosives.