Members of the Maute group have occupied several areas in Marawi City in the restive province of Lanao del Sur, triggering clashes with government troops.
They hoisted ISIS flags at a hospital and several establishments and used a police car with the Daesh flag to block a road.
The attack prompted President Rodrigo Duterte to declare martial law in Mindanao.
Several civilians and soldiers, including a policeman, were reported wounded or killed in the fighting, but local security officials did not release a statement on the clashes.
The 103rd Infantry Brigade also did not issue any statement or reports over the daring attacks by the Maute fighters, whose group had pledged allegiance to the ISIS, and vowed to establish a caliphate in the troubled region.
By Tuesday night, the Western Mindanao Command military headquarters in Zamboanga City said troops clashed with about 15 gunmen in the village of Basak. It said the fighting erupted after Maute members attacked security forces sent to the area following intelligence reports that gunmen were hiding in the village.
However, locals said there were dozens of Maute members scattered in the villages.
A building was also set on fire and electricity cut off, making it extremely difficult for security forces to pursue the militants.
Mayor Majul Gandamra, who is holed out with his security personnel at the City Hall building, said there were no soldiers and policemen in areas where the militants were.
He said he asked the military and police for assistance to help protect City Hall, but no soldiers arrived.
Army Captain Jo-ann Petinglay, a spokeswoman for the Western Mindanao Command, said sympathizers of the Maute group also attacked soldiers triggering a gun battle.
“Government forces were able to contain majority of the militants in one area, however, some of their sympathizers conducted diversionary tactics in other locations to divide the attention of the reinforcing military personnel,” she said.
“Operations are still ongoing and other details cannot yet be revealed so as not to compromise operational security,” Petinglay said. She urged locals to refrain from uploading photos or video clip of soldiers pursuing the militants.
Mujiv Hataman, governor of the Autonomous Region in Muslim Mindanao, condemned “these acts of terror” and said the government stands in solidarity with Marawi “in these dark times.”
“We strongly condemn these acts of terror committed against the people of Marawi City and swear to take immediate action as necessary.
Marawi City is known as the Philippines’ Islamic City, but it is home to people of different histories, different beliefs. That these acts of terror are happening in a diverse community bound by mutual respect and a shared commitment to peace is a travesty,” he said.