MARAWI CITY • Wanted terrorist leader Isnilon Hapilon is believed to have remained in the main battle area in the southern Philippine city of Marawi, contrary to earlier suspicions that he had fled the fighting, said a military official.

Hapilon is a veteran Filipino militant said to be the leader of the Islamic State in Iraq and Syria (ISIS) group in South-east Asia.

A botched attempt by the Philippine government to arrest Hapilon in Marawi in May triggered the rampage by the ISIS-linked Islamist militants who have seized parts of the mainly Muslim city for months.

Asked during an interview with reporters on Wednesday on Hapilon's possible whereabouts, the Western Mindanao Command chief, Lieutenant-General Carlito Galvez Jr, said the notorious Abu Sayyaf leader - with a US$5 million (S$6.8 million) Washington bounty on his head - was still fighting alongside members of the Maute group in the besieged city.

"He is still in the area," Lt-Gen Galvez said, citing the latest information the military had gathered.

In June, Lt-Gen Galvez said there were indications Hapilon might have escaped the battle, adding that there was no sighting of him any more.

There were also reports that Omar Khayyam Maute, one of the Maute siblings who led militants in Marawi, had been killed but these have not been validated so far.

Earlier this week, Captain Jo-Ann Petinglay, the military spokesman in Marawi, said they also received another report that a leader of the militants had been killed.

But Capt Petinglay said they could not say if it was Abdullah Maute, Omar Khayyam's brother.

The fighting, which Lt-Gen Galvez said had so far killed 114 soldiers, was expected to be bloodier as the militants moved inside a shrinking territory.

But he said the military was determined to finish the job.

General Eduardo Ano, the armed forces chief of staff, during a visit to soldiers at the battle front on Wednesday, said the government was winning the battle against the ISIS-inspired militants.

"Just like in the game of basketball, we are already winning but we should not rest on our laurels. We must be more motivated and more persistent," Gen Ano said during a visit to troops at the Kilala detachment inside the war zone.

"Many among our soldiers want to be here to help, but not everyone is given this rare chance to be here, to fight."

PHILIPPINE DAILY INQUIRER/ ASIA NEWS NETWORK