BUTIG, Lanao del Sur -- Troops fired artillery at the town center here on Monday to flush out Islamic militants who have held the impoverished area for three days.

The Maute group bandits, who have pledged allegiance to Islamic State jihadists, fired back as the military advanced, leaving at least one soldier wounded, sources told ABS-CBN News.

The military claims 11 militants have been killed while five others were wounded since fighting erupted on Saturday. Two soldiers suffered shrapnel wounds.

Troops used 105 mm artillery to blast the positions of the Maute group while military SF-260 aircraft dropped bombs over the nearly deserted town.

The relentless pounding of Maute Group positions in Butig, Lanao del Sur. @ABSCBNNews

Thank goodness for earplugs. pic.twitter.com/MuucE0k3I5

— Chiara Zambrano (@chiarazambrano) November 27, 2016

Follow the black dot falling from the sky and listen as SF260s drop 150-lb bombs over the Maute Group in Butig, Lanao del Sur @ABSCBNNews pic.twitter.com/4wHMNzbn8W

— Chiara Zambrano (@chiarazambrano) November 26, 2016

Most of the 17,000 residents of the largely Muslim town on Mindanao island fled to evacuation centers in neighboring towns or to relatives elsewhere after the Maute incursion on Saturday, said Mayor Dimnatang Pansar.

The military also obtained photographs showing the Maute group flying the black IS flag over the old town hall.

LOOK: Black ISIS flag at Butig Town Hall; high school, madrasa, some houses held by Maute Group as defense vs AFP forces | @chiarazambrano pic.twitter.com/WSE3C0mkdE

— ABS-CBN News (@ABSCBNNews) November 26, 2016

Military spokesman Colonel Edgard Arevalo, said this symbolic action was expected from the group.

"They have long been professing allegiance to the foreign terror group. This is still part of the Maute group's agenda in courting support and encouraging similar-minded individuals to support ISIS," he said in a statement.

The Maute group is one of several armed Islamist organisations in Mindanao which have pledged allegiance to ISIS fighters in Iraq and Syria.

In past clashes with troops, its members were seen carrying black IS flags and bandannas bearing the jihadists' insignia were found in their base, the military said.

Three members of the Maute group were arrested last month, accused of the September bombing that left 15 people dead in Davao, Duterte's home town and Mindanao's largest city.

The Maute group, once described by the military as a small-time extortion gang, attacked a remote army outpost in Butig in February, triggering a week of fighting that the military said left six soldiers and 12 militants dead.

The group also beheaded two employees of a local sawmill in April, the military has said. -- Reports from Chiara Zambrano, ABS-CBN New; Agence France-Presse