11 ISIS sympathizers have reportedly been killed in a siege in the southern Philippines

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A US Marine stands guard as a passenger truck passes by April 29, 2002, in Lamitan town on Basilan Island, southern Philippines.

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

The Maute Group, one of a handful of small militant 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 the black Islamic State flag in the hall, Marine Colonel Edgard Arevalo, a military spokesman, said, according to Reuters.

"This was expected since they have long been professing allegiance to the foreign terror group," he said. "This is still part of the Maute Group's agenda in courting support and encouraging similar-minded individuals to support ISIS (Islamic State)."

According to Philippin journalist Chiara Zambrano, reporting from the location of the fighting, Maute Group rebels were able to raise the ISIS flag above Butig Town Hall.

The rebels reportedly held the town hall in addition to taking control of a madrasa, a high school, and some houses.

Two Philippine soldiers were hurt by shrapnel from a rocket-propelled grenade and had to be evacuated from the scene of the fighting, Zambrano reported. The Philippine armed forces also used air-dropped 150-pound bombs and artillery during the clash with the Maute Group, according to footage captured by Zambrano.

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. Though the Philippines is predominantly Catholic, many people in the south are Muslim.

The government has blamed the Maute Group for a September 2 bombing at a street market in the hometown of Philippine President Rodrigo Duterte, which killed 14 people and wounded dozens. In the wake of that bombing, Duterte put a nationwide "state of lawless violence" in place, increasing the presence of the military and police around the country.

Several suspected group members were arrested a month later and, according to the defense minister, video clips were found of them pledging loyalty to the Islamic State cause.

Erik De Castro/Reuters

Philippine President Rodrigo Duterte makes a "fist bump," his presidential campaign gesture, with defense officials and female soldiers during a visit at Capinpin military camp in Tanay, Philippines, August 24, 2016.

Duterte has recently been warning about Islamic State taking root in the Philippines and said his country needed to avoid "contamination."

"What we are afraid of is if the ISIS are forced out (of Iraq and Syria) and if (they) lose the land mass, they will try to come to Indonesia, Malaysia and the Philippines because they have declared the caliphate," he said in a speech late on Saturday, according to Reuters.

Duterte has floated the idea of suspending the writ of habeas corpus - which gives an arrestee the right to contest their detention in front of a court - in response to violence and lawlessness in the country.

In mid-November, the president said human-rights concerns could become an afterthought if the Islamic State began operating in the Philippines.

"Remember, these guys, they do not have an iota of what is human rights, believe me," he said. "I will not just simply allow my people to be slaughtered for the sake of human rights, that's bulls---."

(Reporting for Reuters by Enrico dela Cruz; editing by Martin Petty and Mark Potter)