DNA tests have confirmed the death of one of the FBI's most-wanted terror suspects, who the Philippine military reported was killed in a final battle to quell an Islamic State group-linked siege in southern Marawi city, U.S. and Philippine officials said Saturday.

U.S. Embassy spokeswoman Molly Koscina told The Associated Press that DNA tests done in Virginia at the request of the Philippine military confirmed the death of Isnilon Hapilon. Washington has backed efforts by the Philippines, a treaty ally, to combat terrorism for years.

"This is yet another example of how the U.S. is supporting our friend, partner and ally in the fight against terror," Koscina said.

Hapilon and Omarkhayam Maute, another leader of the Marawi siege, were killed in a gunbattle Monday in a push by thousands of troops to retake the last pocket of the Islamic city held by the militants, Defense Secretary Delfin Lorenzana said.

The Philippine military believes that Mahmud bin Ahmad, a top Malaysian militant and close associate of Hapilon, had also been killed in the Marawi clashes, although his body has yet to be recovered by troops.

DNA tests were also being done on the remains of other suspects who have been recovered by troops, Lorenzana said without elaborating.

The confirmation of the deaths of Hapilon and Maute would pave the way for the payment of huge U.S. and Philippine bounties offered for the two. A rescued 16-year-old hostage provided the crucial information that allowed troops to locate Hapilon and Maute in one building in Marawi, Lorenzana said.

The U.S. State Department has offered a reward of up to $5 million for Hapilon, who Washington blames for ransom kidnappings of several Americans, one of whom was beheaded in 2001 in southern Basilan province. Hapilon had been indicted in the District of Columbia for his alleged involvement in terrorist acts against U.S. nationals and other foreigners.

A soft-spoken Islamic preacher born to a family of militants on southern Basilan island, Hapilon had been linked to several major attacks in the southern Philippines, including kidnappings, bombings and attacks on urban centers.

Hapilon and Maute were among the leaders in a nearly five-month insurrection in the lakeside city that has left at least 1,127 people dead, including 915 militants and 165 soldiers and police.

The siege has sparked fears that the Islamic State group may gain a foothold in Southeast Asia by influencing and providing funds to local militants as it suffers battle defeats in Syria and Iraq.

The United States and Australia have deployed surveillance aircraft to help Filipinos battling the Marawi attackers.