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ISIS flagReuters

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 (ISIS) group-linked siege in southern Marawi city, U.S. and Philippine officials said Saturday, according to The Associated Press.

U.S. Embassy spokeswoman Molly Koscina told AP 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 told the news agency.

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

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

The ISIS-affiliated jihadists seized Marawi in May, where they have reportedly brutalized and beheaded civilians.

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, noted AP.

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

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