US special forces are assisting Philippine troops in their operations against Islamic militants in the southern city of Marawi, the USA embassy in Manila said in an emailed statement. In 2002, the U.S. helped Philippine authorities track down Abu Sayyaf leader Abu Sabaya, who was killed in that operation.
Al Jazeera's Jamela Alindogan, reporting from the Philippine capital of Manila, said that despite Duterte's hostile declarations, the United States military's assistance "comes as no surprise because".
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.
He said they were killed during an "intense firefight" on Friday as they were conducting operations to clear enemy positions.More news: British PM, rival face angry voters as election nears
The military earlier released a video of Hapilon and cohorts plotting attacks around Marawi City days before the siege began.
The latest casualties bring the number of Philippine troops killed in the fighting to 58.
In Marawi, military spokesman Lieutenant Colonel Jo-Ar Herrera confirmed the US assistance, telling a news conference: "They are not fighting. They are just providing technical support", he said.
"We are still awaiting confirmation", military spokesman Lieutenant Colonel Jo-Ar Herrera told a news conference in Marawi City. It's unclear how many people remain trapped in Marawi as government troops battle Muslim militants led by the so-called "Maute" group but army officers have put the figure this week at anywhere from 150 to 1,000.More news: Oregon tops LSU 4-1, will play Oklahoma in WCWS semifinals
President Rodrigo Duterte had earlier threatened to throw out USA troops amid strained relations since taking office.
United States troops will not fight, but provide technical support, Philippines military say.
But Duterte has openly scorned the alliance, seeing it as an obstacle to a rapprochement with China, and has repeatedly lambasted Washington.More news: Rain plays spoilsport in New Zealand-Australia encounter at Edgbaston
A U.S. Navy aircraft provided surveillance for the local troops as the battle raged in Marawi on Friday, confirming the involvement of the U.S. military in helping quell the urban insurrection at the request of the Philippine government, Philippine military officials said.