MANILA (REUTERS) - Four pro-ISIS militants were killed in air strikes by Philippine troops in a southern province where the rebel group launched a Christmas Day attack, a military spokesman said on Tuesday (Dec 26).

Members of the Bangsamoro Islamic Freedom Fighters (BIFF) attacked Datu Unsay town in Maguindanao on Monday, burning two houses and prompting residents to flee, said Captain Arvin Encinas, spokesman for the 6th Infantry Division.

The latest military operation follows last month's shelling of BIFF gunmen in support of ground attacks in an area of marshland between the provinces of Maguindanao and Cotabato, about 170km from Marawi City.

The shellings took place as the military pushes on with a new offensive after the country's biggest urban battle in decades in Marawi, which was occupied for several months by Islamic State in Iraq and Syria (ISIS) loyalists including BIFF fighters.

The militants' occupation of Marawi and their dogged resistance spread alarm in the region over the rise of extremism and radical aspirations to create an ISIS caliphate.