MANILA, May 29 (Xinhua) -- The Philippine defense chief expressed optimism on Monday that all Islamist militants inside Marawi City will be flushed out by June 1, or by Thursday this week.

In a text message to defense reporters, Defense Secretary Delfin Lorenzana said the target is to clear the southern Philippine city on Mindanao island of the remnants of Maute militants linked to the Islamic State group that tried to occupy the city on May 23.

"(The) timetable is one week from May 25," Lorenzana said, adding that he is being updated by developments in the besieged city.

The militants launched the siege to establish a caliphate in that part of Mindanao, according to Philippines authorities.

Lorenzana said the government troops "are on track" in meeting the June 1 deadline.

Brig. Gen. Resituto Padilla, the spokesman for the Armed Forces of the Philippines (AFP), told a news conference that the Philippine military is capable of conducting "surgical air strikes" to defeat the militants.

Col. Edgard Arevalo, the AFP public affairs chief, said security remains tight in and around the city as soldiers and police try to contain the remaining militants in the city.

He said the troops are "using precision ammunition" in conducting surgical airstrikes.

"This means that we have well-identified targets and we have highly skilled and trained pilots delivering the payload to our targets," Arevalo said.

Specifically, he added the airstrikes are intended "to destroy enemy positions that are preventing security forces from advancing and clearing the remaining pockets of resistance and in rescuing civilians still trapped in the city."

Residents of Marawi have fled to nearby Iligan City since clashes broke out last Tuesday afternoon.

Myrna Jo Henry, the information officer at the Autonomous Region in Muslim Mindanao's Humanitarian Emergency Action and Response Team, said the armed conflict has displaced more than 17,000 families or nearly 85,000 residents.

The city is home to more than 200,000 residents. She said the evacuees are now housed in 19 centers, two in Marawi City and 17 in Iligan City and other towns in Lanao del Sur province.