Bomb blasts rocked the besieged Philippines city of Marawi on Monday as the national flag was hoisted to celebrate Independence Day and the recapture of the city hall.

Tearful rescue workers, soldiers and firemen sang the national anthem and listened to speeches at the first flag raising in the southern city since May 23, when the twice-weekly ceremony was halted by a massive siege on the city by Islamist fighters.

During Monday's ceremony, three OV-10 attack aircraft dropped bombs on the areas where fighters were still holed up, while gunshots rang out across the mostly-abandoned city.

"This is dedicated to soldiers who offered their lives to implement our mission in Marawi city," said Colonel Jose Maria Cuerpo, commander of a Philippine Army brigade fighting in Marawi.

US-backed offensive

Thousands of Philippine soldiers, now advised by US Special Forces and US reconnaissance aircraft, have been battling with several hundred insurgents who overran the city last month, flying black flags of the so-called "Islamic State ('IS')."

Almost all of the 200,000 residents fled from the lakeside town on the Philippines' southernmost island of Mindanao, but between 500 and 1,000 civilians remained trapped. Philippine President Rodrigo Duterte declared martial law on the island to help combat the militants.

At least 58 soldiers and police were killed in fighting along with at least 20 civilians, the military said, estimating that almost 200 militants had been killed in the clashes.

"To our Muslim brothers there, we want to tell them to stop their meaningless fight because we are all Muslims," Vice Provincial Governor Mamintal Adiong Jr. told the gathering.

Human shields

The military had hoped to end the siege by Independence Day, but on Monday troops were still struggling to reach the downtown area where militants were using about 100 hostages as human shields, hiding in mosques and using a pre-existing bomb-proof underground tunnel network, officials said.

"As you know the target was to liberate Marawi today, June 12, but ... you can see how complex the problem is and how many new developments there are," Foreign Secretary Alan Peter Cayetano told reporters in Manila.

Duterte said on Sunday he had not expected the battle to be as serious as it became, adding it had now emerged "that Baghdadi himself, the leader of 'IS', has specifically ordered terroristic activities here in the Philippines".

Foreign Affairs Minister Allan Peter Cayetano said in a speech in the capital Manila that the militants had planned to take over at least two or three cities in Mindanao, but were foiled by a preemptive raid on Marawi to capture Isnilon Hapilon, leader of the Abu Sayyaf group and 'IS's "emir" of Southeast Asia.

"We want to coordinate very well with Indonesia and Malaysia so they won't also suffer in the hands of extremists," he said.

"But the president knew at the start of his term that, as the allies become more successful in Syria and Iraq, 'IS' will be looking for a land base, and Indonesia, Malaysia and the Philippines will be a potential target to them."

In Manila, Duterte skipped the flag-raising rites at Rizal Park, citing fatigue.

On Monday China said it supported the Philippines' "anti-terrorism" operations after the US embassy confirmed it that US special forces were assisting in the operations.

"Terrorism is the common enemy of mankind. China understands and firmly supports Duterte's leadership and its government in fighting terrorism," Chinese foreign ministry spokesman Lu Kang told a regular press briefing.

aw/rt (AFP, dpa, Reuters, AP)