Thirteen Philippine marines have been killed in a gun battle with Islamist militants as troops step up an offensive to regain control of a southern city besieged by the terrorists for nearly three weeks. In 2002, the U.S. helped Philippine authorities track down Abu Sayyaf leader Abu Sabaya, who was killed in that operation.
In a press briefing, Lt. Col. Jo-ar Herrera said that United States special forces were helping the army.
For the past 18 days, boys such as these and their adult commanders have occupied the centre of Marawi, a city of 221,000 people in the southern Philippines.
Military casualties stemmed from intense, house-to-house fighting and the militant's use of improvised explosive devices, Herrera added.More news: Thiem stuns Djokovic to reach semi-finals
In Marawi, military spokesman Lieutenant Colonel Jo-Ar Herrera confirmed the US assistance, telling a news conference: "They are not fighting".
Before the confirmation, a USA spy plane was seen flying over Marawi.
The cooperation between the longtime allies is significant because President Rodrigo Duterte, who came to power a year ago, has taken a hostile stance toward Washington and has vowed to eject USA military trainers and advisers from his country.
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% of the city. "American forces have always been present - although they are there primarily for technical and intelligence support".
Until now there had been no confirmation that the Philippines had sought United States support in the battle for Marawi City on the island of Mindanao, which is in its third week.More news: Third London Bridge attacker named
The little-known Maute group has been a fierce enemy of a military with superior firepower and greater troop strength.
"The presence of our USA counterparts facilitates exchanges of intelligence ... and also provides training exchanges and, of course, the technical support that we are sharing together in the fight against global terrorism", he added.
It added that Washington would "continue to work with the Philippines to address shared threats to the peace and security of our countries, including on counterterrorism issues".
Police said one of the latest fatalities was a 15-year-old boy killed by a stray bullet attributed to a militant sniper while praying inside a mosque.More news: 5 dead as storm brings some relief to drought-hit Cape Town