(CNN Philippines, May 23) — Government forces clashed with members of the rebel group Maute in Marawi City, Lanao del Sur on Tuesday.

Reports said armed men have taken over the Amai Pakpak Medical Center, with the group allegedly replacing the Philippine flag with a black flag, supposedly representing the Islamic State (ISIS).

They have also reportedly blocked checkpoints in the vicinity.

Armed Forces of the Philippines (AFP) First Infantry Division Spokesman Lt. Col. Jo-Ar Herrera said the firefight started 2 p.m. at Barangay Basak Malutlut.

"Nakatangap po tayo ng report from the community, meron silang nakitang mga armado...na-check po natin na ito pala yung ano, yung core group ng Maute, so nag-launch po tayo ng surgical operation para i-neutralize 'yung grupo na may planong mag-ano ng terorismo sa Marawi City," Herrera said.

[Translation: We received a report from the community, they saw armed men…we checked that this is the core group of Maute, so we launched a surgical operation to neutralize the group planning to incite terrorism in Marawi City.]

He added Abu Sayyaf leader Isnilon Hapilon was among the 15 armed men seen in the area.

Herrera said while firefight has ended, clearing operations are still ongoing, as at least five members of the government force sustained injuries.

Redoble Adonis of Camp Ranao said a group inspired by ISIS attacked the 103rd Brigade, situated at Camp Ranao in Marawi City.

"The AFP members directly blocked their way resulting to exchange of fire. Accordingly, not less than 500 members of Maute (Isis) tried to penetrate the camp. GT Marawi situated at Campo Ranaw, Marawi City is about 300 meters from the place of the attacked," Adonis said.

However, AFP spokesman Brig. Gen. Restituto Padilla said a combined military and police force initiated the operation in Marawi.

"We received reliable info on Hapilon and a number of his cohorts. Updates to follow as the operation is still ongoing," Padilla said.

Marawi City Mayor Majul Gandamra told CNN Philippines' News Night the hospital under siege is just about 2 km away from the city hall.

"Right now, based on initial information, no casualties reported...we are coordinating with the military, wala po silang casulaties na sinabi," Gandamra said.

There are eyewitness reports that the Marawi City Jail and the Dansalan Junior College were on fire.