US special forces are helping the Philippines military retake the southern city of Marawi from IS-linked militants, the army said on Saturday.

In a press briefing, Lt. Col. Jo-ar Herrera said that US special forces were helping the army. 

"They are not fighting. They are just providing technical support," he said.

President Rodrigo Duterte had earlier threatened to throw out US troops amid strained relations since taking office.

The militants have been under siege since rampaging through the southern city on May 23. The latest fighting has claimed the lives of 13 Philippines marines, BBC reported.

Hundreds of militants, flying the black flag of the Islamic State and led by the self-styled IS emir of southern Philippines, Isnilon Hapilon, and the Maute brothers Omar and Abdullah, were still holed up in the city.

The fresh army fatalities raised the death toll from the government side to 58, while 138 extremists and 21 civilians were also killed.

Since fighting began, the army has taken back 90 per cent of the city.

Duterte declared martial law in the entire Mindanao region the day the conflict broke out.