Four pro-Islamic State militants were killed in airstrikes by Philippine troops in a southern province where the rebel group launched a Christmas Day attack, a military spokesman said on Tuesday.

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 170 km (106 miles) 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 loyalists including BIFF fighters.

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