Fighting continues in the town of Butig, two days after the Maute Group took over a local town hall.

Government troops have killed at least 11 members of a rebel group in the southern Philippines that has pledged allegiance to the Islamic State of Iraq and the Levant (ISIL) group, the military said, sending local communities fleeing as a battle raged on Sunday.

The Maute Group, one of a handful of small armed groups behind years of unrest in the south, had since Saturday occupied parts of a municipality in Lanao del Sur and were holed up in an abandoned town hall.

At least four soldiers were wounded in the clashes and there were unconfirmed reports that the group had raised an ISIL flag in the hall, said Marine Colonel Edgard Arevalo, a military spokesman.

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

Al Jazeera’s Jamela Alindogan, reporting from Manila, said that the fight was ongoing with the town of Butig beseiged and about 200 members of the Maute Group there.

“The leaders of this group are believed to have some foreign fighters who are also a part of this siege,” Alindogan said.

“They also took control of a high school and a mosque in the same town, now half of those residents have already fled and half of them remain to be stuck in that village, this is an operation that is expected to last for days.”

The military has not given an estimate for the number of displaced but local media reported an exodus of as many as 16,000 people from the area. Though the Philippines is predominantly Catholic, many people in the south are Muslim.

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The Maute group is one of several armed organisations in the Mindanao islands that have pledged allegiance to ISIL.

“Maute came from a name of a clan that is very influential and powerful in Boutig,” Al Jazeera’s Alindogan said. “President Rodrigo Duterte has said in the past that they would like to talk to the Maute Group, but the military has already named them as a terror group.

The 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 army said left six soldiers and 12 fighters dead.

The black ISIS flag at Butig Town Hall. High school, madrasa, some houses held by Maute Group members as defense vs AFP forces @ABSCBNNews pic.twitter.com/DWgO0t06iB — Chiara Zambrano (@chiarazambrano) November 26, 2016

The group also beheaded two employees of a local sawmill in April, according to the military.

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

Government forces captured a Maute training camp in the town in June after a 10-day gunbattle that killed four soldiers and dozens of fighters, according to an army account.