US forces back Philippine troops in Islamist held city

Marawi : United States special forces are providing support to the Philippine military battling to dislodge Islamist militants in a southern city, the US embassy said Saturday, as 13 Filipino marines were killed in fresh fighting.

Philippine troops are struggling to defeat hundreds of fighters, who rampaged through Marawi on May 23 flying black flags of the Islamic State group, and have used bomb-proof tunnels, anti-tank weapons and civilians as human shields to fortify their positions.

Friday's ferocious, street-to-street gunbattles with the militants saw 13 troops killed in a dramatic surge in the toll from the conflict.

It was among the heaviest fighting in the standoff, according to AFP journalists in Marawi, with the air force supporting ground troops with sustained bombing runs that battered the city.

As the fighting intensified, the US embassy in Manila said American forces were providing assistance to the Filipino troops, although it declined to give details for security reasons.

"At the request of the government of the Philippines, US special operations forces are assisting the (Philippine military) with ongoing operations in Marawi," the embassy said in a statement.

Philippine military spokesman Lieutenant Colonel Jo-ar Herrera confirmed the US help, adding that the special forces were not fighting, but "providing technical support".

He said Friday's deaths brought the number of government troops killed in the conflict to 58.

"There were intense firefights, house-to-house gunbattles," said Herrera at a news conference in Marawi.

"We are saddened with the result... we have fatalities on the government side," he said.

At least 20 civilians and around 138 militants have also been killed, the government said.

The insurgents have so far withstood more than two weeks of air and ground assaults by security forces, with about 2,000 people believed to be trapped in militant-held areas although the military said this amounts to only around 10 percent of the city.

Herrera said the militants' tactics was making it harder for security forces to carry out attacks without causing civilian casualties and hurting religious sensitivities.

"The local terrorist groups are using the mosque, they are entrenched there. They also used civilians as human shields... we are very precise in our operations to avoid collateral damage."

President Rodrigo Duterte said the militant attack was part of a wider plot by IS to establish a base in the southern region of Mindanao, and declared martial law there to quell the threat.

The announcement of US help in the embattled southern region comes after Duterte has sought to reduce the Philippines' reliance on the United States and build much closer ties with China and Russia.

The US Embassy said Washington would "continue to work with the Philippines to address shared threats to the peace and security of our countries, including on counterterrorism issues" in its statement Saturday.