Now, what sound like 155mm cannons firing in the same direction pic.twitter.com/Bizfju4Nwb

— Chiara Zambrano (@chiarazambrano) November 28, 2016

A third wounded soldier being airlifted from the frontlines. Intense fighting this AM in an attempt to retake Butig town from Maute Group pic.twitter.com/jnmoo7y5Be

— Chiara Zambrano (@chiarazambrano) November 28, 2016

BUTIG - More than 16,000 residents of Butig, Lanao del Sur have fled their homes as military troops continue to fire artillery at Maute Group positions in this town Monday.

Butig Mayor Jimmy Pansar said about 16,000 residents have been evacuated since the fighting started.

Disaster officials said 1,955 families have been given relief packs.

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

Troops used 105 mm artillery to blast the positions of the Maute group in the nearly deserted town of Butig in the third day of fighting since the gunmen -- who claim allegiance to the Islamic State group -- occupied Butig's abandoned town hall.

EXCLUSIVE: In a chilling attempt to demonstrate control, members of the terrorist Maute Group - cloaked in black - are photographed lowering the Philippine flag of the Butig Municipal Hall, replacing it with the black flag of ISIS. This is the same town hall attacked by the Maute Group last February 2016. A madrasa and a national high school, also in Butig, have also been occupied by the Maute Group, to ward off the military. @abscbnnews

A photo posted by Chiara Zambrano (@chiarazambrano) on Nov 26, 2016 at 5:25am PST

Mortar bombs could be heard in the distance as an MG-520 helicopter gunship flew overhead, a reporter in the town said.

Four soldiers were wounded in today's clashes with the Maute Group, bringing to nine the number of soldiers wounded since Saturday.

Armed Forces spokesman Brigadier General Restituto Padilla, citing what he called "intelligence sources", earlier said 11 of the militants had been killed and five wounded.

Padilla said their bodies had not yet been recovered.

Reporters in Butig said the military had obtained photographs showing the Maute group flying the black IS flag over the old town hall.

However they themselves were not allowed to get close enough to verify this.

PFC Abuid, hit by RPG shrapnel on arm, did not want to be taken out of the frontline. "Ok lang ako. Kanina masakit pero hindi na ngayon." pic.twitter.com/0pJz3zCCtD

— Chiara Zambrano (@chiarazambrano) November 27, 2016

Another military spokesman, Colonel Edgard Arevalo, said this symbolic action was expected.

"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, using another acronym for IS.

The Maute group is one of several armed Islamist organisations in Mindanao which have pledged allegiance to Islamic State 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.

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

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. With a report by Agence France-Presse