MARAWI, Lanao del Sur - Sounds of gunshot and blasts pierced the heart of this southern city anew on Thursday, just a day after the military said it has succeeded in driving rebel forces to Marawi's fringes.

ABS-CBN sources said the rumble of fighting came some 500 meters away from the Lanao provincial capitol, located in the town center.

Black-clad Maute and Abu Sayyaf bandits were also reportedly spotted in major roads and bridges, where military reinforcements are set to pass through.

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Authorities however have yet to confirm if the extremists had succeeded in regrouping and securing back-up forces.

The pandemonium in Marawi first erupted on Tuesday, after extremists torched several buildings and battled state forces, leaving 7 state troops and 13 Maute fighters dead.

President Rodrigo Duterte has declared martial law in the entire Mindanao on the same day.

On Wednesday, the military announced that the extremists have fled and that the government has recaptured the city hall, the Mindanao State University, and the Amai Pakpak Medical Hospital.

A lull in the fighting then allowed Marawi residents to flee to the neighboring towns of Iligan and Cagayan de Oro in droves.

Areas where the skirmishes started remained "ghost towns" on Thursday, ABS-CBN sources said.

Narrow streets were empty of motorists. Pavements meanwhile were littered with hastily abandoned stalls and various goods.

The few residents who chose to stay in Marawi were mostly those whose houses were located near the military camp.

The military has ruled out using airstrikes to flush out rebels for the sake of the remaining civilians.