Islamic gunmen have held the Philippine army at bay, burning buildings, taking at least a dozen hostages and sending tens of thousands of residents fleeing. Officials say the commander, Isnilon Hapilon, who is one of Washington’s most-wanted militants, is still hiding somewhere in the city.

President Rodrigo Duterte declared martial law in the south through mid-July after the militants went on a deadly rampage in Marawi last week following an unsuccessful military raid to capture Hapilon.

Rohan Gunaratna, a terrorism expert at Singapore’s S. Rarajatnam School of International Studies, believes that IS and the smaller regional groups are working together to show their strength and declare a Philippine province part of the caliphate that IS says it created in the Middle East.

He said the fighting in Marawi, along with smaller battles elsewhere in the southern Philippines, may be precursors to declaring a province, which would be “a huge success for the terrorists.”