BUTIG, Lanao del Sur -- (2ND UPDATE) Fifteen terrorists accompanying Isnilon Hapilon, an extremist leader with alleged links to the Islamic State, have been killed in the ongoing airstrikes here, the Armed Forces of the Philippines confirmed Sunday.

AFP Public Affairs chief Col. Edgard Arevalo said the fatalities belong to Abu Sayyaf group led by Hapilon, and the Maute terror group.

Among the fatalities, he added, was an Indonesian national identified only as alias Mohisen.

Two other local terrorists were also injured with one identified as Sahl Num.

The military offensives also wounded 8 terrorists, including Hapilon himself, who is on the United States' list of "Most Wanted Terrorists."

Hapilon was "seriously wounded" and was still being carried by 4 men in a makeshift stretcher as of Friday, Defense Secretary Delfin Lorenzana earlier said.

Hapilon, also known as Abu Abdullah, might die as he needed immediate medical treatment, military chief General Eduardo Ano told reporters, citing intelligence and communications intercepts.

"He needs blood transfusion. Without proper medical treatment, he may die," Ano said.

Hapilon is believed to be hiding in the mountains of Butig, Lanao del Sur, the military said.

The AFP is also not yet counting the operation as a success since Hapilon has been declared dead several times over the years.

Ano also said they were still "digging and doing more investigation" about the Indonesian's background. Hapilon was with two other foreigners whose nationality was uncertain, he said.

Troops continued to fire artillery at positions held by Hapilon's group on Sunday morning.

No one was reported injured or killed from the military so far.

The 50-year-old Hapilon is a senior leader of the Abu Sayyaf, a notorious kidnap-for-ransom gang based in Mindanao, and security analysts say the IS has recognized him as its leader in Southeast Asia.

The Abu Sayyaf, a loose network of militants formed in the 1990s with seed money from Al-Qaeda, preys on vessels in the waters between Malaysia, Indonesia and the Philippines and has earned millions of dollars from kidnappings-for-ransom.

Hapilon has a $5-million bounty on his head from the US government due to his involvement in the 2001 kidnapping of 3 Americans in Palawan.

The militants beheaded one captive in their stronghold in Basilan, while another hostage died in the crossfire with soldiers during a rescue operation in 2002. The third American was freed.

Hapilon has pledged allegiance to IS, which has endorsed him as "emir for Southeast Asia," according to a 2016 report by the Jakarta-based think-tank Institute for Policy Analysis of Conflict.

"Southeast Asians in Syria have pledged their loyalty to him," the report said.

Hapilon was based in Basilan but Lorenzana said this week that he had moved to Lanao del Sur province in a bid to establish an IS presence there.

Lorenzana added Hapilon was "trying to rally" into cooperation the Maute group, another gang which had pledged allegiance to IS.

• READ: Islamic State pushing for Asian links, expansion, PH says

-- With reports from Chiara Zambrano, ABS-CBN News; Agence France-Presse and Reuters