The United States played a "very important role" in defeating Islamic State (IS) supporters who occupied parts of a southern Philippine city for 5 months, the US ambassador in Manila said Thursday.

Ambassador Sung Kim highlighted American intelligence, urban warfare training, and drones as among the factors that helped end the conflict in Marawi city on Monday, which local authorities said claimed more than 1,100 lives.

"We did play a very important role in supporting the (Philippines') efforts to retake Marawi," Kim told reporters.

"We had P-3s (surveillance planes), Grey Eagles (drones) providing crucial intelligence information to the Armed Forces of the Philippines so that they would be able to carry out operations necessary to retake Marawi."

He also said US forces provided "very useful technical advice," especially in the area of urban warfare where they had more experience than Filipino troops.

The United States also provided guns, ammunition and rubber boats to the Philippine military, while committing 750 million pesos ($14.7 million) in aid to residents forced out of their homes because of the war, Kim said.

He said the United States had about 100 to 200 troops based in the southern Philippines to train and advise local forces in battling Muslim extremists, but he would not elaborate on their role in Marawi.

The United States and the Philippines are longtime allies, with the nations bound by a mutual defense pact.

However, Philippine President Rodrigo Duterte, a self-described socialist, has sought to loosen his nation's alliance with the United States in favor of closer ties with China and Russia.

Duterte last year cursed then-US President Barack Obama and said he planned to cancel all military exercises with the United States.

His anger was partly driven by American criticism of his crackdown on drugs, which has seen police kill over 3,800 people in anti-drug operations and led rights groups to warn that Duterte may be orchestrating a crime against humanity.

However, relations have improved under Obama's successor, Donald Trump, who has praised Duterte for his drug war.

Kim said Thursday that US-Philippine ties were "back to normal," and cited a resumption of regular joint military exercises.

He also said the United States was not concerned about the Philippines' deepening relationship with China and Russia, which has seen them for the first time provide significant amounts of military hardware.

"I'm not in any way threatened by the fact that China and Russia are also providing military assistance to the Philippines," Kim said.