The military has warned there would be "collateral damage" as they deployed SF-260 close-air-support planes to back attack helicopters.
Troops have cleared nearly 90 percent of Marawi city, where the gunmen linked to the Islamic State group have been fending off government troops since a botched raid to capture a veteran rebel leader triggered a militant siege, said military spokesman Brig.
The rebels hold about a tenth of the city, the army said.
"They were able to get an armoured vehicle of the police".
Military spokesmen said fighting alongside the militants are prisoners they freed from the city's two jails last week and an unknown number of foreign fighters. "Yes indeed, there was planning involved", he added.
The military has, from the outset, insisted it has control of the situation, but the slow pace of efforts to retake Marawi has prompted questions about its strategy, Reuters reported.
This image made from undated militant video which could not be independently verified shows Father Teresito Suganob.
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Meanwhile, the troops have killed 89 militants during the urban battles, AFP reported authorities as saying.
"We call on the remaining terrorists to surrender while there is an opportunity", Brigadier-General Restituto Padilla said.
"That 10 percent is most likely the area that is heavily guarded and defended by any armed men if they are protecting any individual of high value".
"The propaganda of the enemy...is indicative if their fighting for survival".
Duterte, who declared martial law in Mindanao, has approved the creation of a "peace corridor" to hasten the rescue of civilians and delivery of humanitarian aid for displaced persons, said presidential spokesman Ernesto Abella.