The Philippine armed forces declared an eight-hour ceasefire Sunday in its ongoing offensive against Islamist militants occupying parts of the war-torn city of Marawi to allow residents to celebrate the end of Ramadan.

Military chief General Eduardo Ano said his forces would implement a "humanitarian pause" during the Eid al-Fitr holiday in Marawi, which is considered the most important Muslim city in the mainly Catholic Philippines.

"We declare a lull in our current operations in the city on that day as a manifestation of our high respect to the Islamic faith," Ano said in a statement.

The Eid al-Fitr feast ends the fasting month of Ramadan when observant Muslims do not drink or eat between dawn and nightfall.

The general described the move as "a testimony to the Armed Forces of the Philippines' solid commitment to provide our brother Muslims, especially in the city of Marawi, an opportunity to observe this festive event."

Hundreds of militants flying the Islamic State group flag and backed by foreign fighters seized swathes of Marawi in the southern region of Mindanao last month, sparking an ongoing bloody, street-to-street battle.

In May Philippine President Rodrigo Duterte declared martial law across all of Mindanao to quell what he said was a rebellion aimed at establishing an IS province in the area.

Government troops have launched a relentless air and ground offensive in a bid to crush the militants but have failed to dislodge gunmen from entrenched positions in pockets of the city.

Much of the lakeside city is now in ruins while most of its 200,000 residents have fled to evacuation centres or to the homes of relatives and friends.

Source: AFP