President Rodrigo Duterte, second right, wearing a bull cap and an assault rifle slung on his shoulder, walks with other military officers and security men inside the camp of the 2nd Mechanized Infantry Brigade, Light Armored Division, in the outskirts of Iligan city in southern Philippines, on Friday.

:: Snipers in high-rise buildings are the main problem facing Philippine forces battling to crush pro-Daesh (the so-called IS) fighters who have occupied a southern city for more than a month, a military spokesman said on Saturday.

Lieutenant Colonel Jo-ar Herrera said this was the reason the government was using air strikes against the militants despite the massive damage it may cause in the city of Marawi.

“If we do not use air strikes, we will incur more casualties of our troops,” he told reporters in Marawi, which was overrun by hundreds of militants on May 23.

Despite more than a month of fighting with hundreds of government troops, militants flying the black flag of Daesh are still entrenched in parts of the city.

The military has used jet fighters, attack planes and helicopter gunships, armed with bombs and rockets, to attack areas where the gunmen are hiding.

“We have identified key defensive positions. These are being subjected to surgical air strikes now. They are still occupying high-rise buildings. We need to take them down so we can facilitate a swift offensive of our troops,” Herrera said.

“One reason we are using air assets… is this is the advantage we need to neutralize the snipers’ positions,” the regional military spokesman added.

“They occupy high-rise buildings so we have to be higher. So we use air strikes.”

While hundreds of fighters rampaged through much of Marawi in the early days of the siege, Herrera said there were now around 80 gunmen still active in the “main battle area” comprising around 800 buildings.

“These are the tall buildings. This was the center of commerce of Marawi City,” he explained.

However the buildings also needed to be cleared of improvised bombs and other booby-traps as the troops advance, he said.

There are also about 300 civilians trapped in the area, Herrera said, adding that some were being used as hostages, bearers of supplies and even being forced to help in looting the city.

President Rodrigo Duterte last month vowed to “crush” the militants, but several deadlines have already been missed to end a conflict that has forced almost 400,000 people from their homes.

The fighting has reduced Marawi, considered the Muslim capital of the largely Catholic Philippines, to a ruined ghost town. It also prompted Duterte to declare martial law over the entire southern Philippines.

Herrera said 366 enemy fighters, 39 civilians and 87 government troops had been killed in the fighting so far.