The head of ISIL's branch in South-East Asia, who figures on the US "most wanted terrorists" list, has been killed in the battle to reclaim a militant-held Philippines city, the country's defence minister said on Monday.
Isnilon Hapilon's death came during the fifth month of a battle to end a militant siege of Marawi, which has claimed more than 1,000 lives and raised fears that ISIL was attempting to establish a regional base in the southern Philippines.
Philippine troops "were able to get Isnilon Hapilon and Omar Maute. They were both killed," said defence secretary Delfin Lorenzana, referring to another militant leader whose fighters took part in the attack on Marawi in May.
President Rodrigo Duterte and security analysts say Hapilon has been a key figure in the extremist group's drive to establish a South-East Asian caliphate as they suffer battlefield defeats in Iraq and Syria.
The US government had offered a US$5 million (Dh18m) bounty for information leading to Hapilon's arrest, describing the 51-year-old as a senior leader of the southern Philippines-based Abu Sayyaf group, which the US considers a "foreign terrorist organisation".
Mr Lorenzana said Philippine ground forces mounting a final assault on the militants in Marawi killed Hapilon and Omarkhayam Maute, one of two brothers who led a militant group allied to Hapilon, early on Monday.
DNA tests will be carried out on the two bodies because of the reward offer from the US and Philippine governments, he added.
"The implication of this development is that the Marawi incident is almost over and we may announce the termination of hostilities in a couple of days," Mr Lorenzana said.
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Philippine authorities have made several previous announcements on the imminent end of the conflict, but observers believe this time the forecast is likely to be accurate.
Pro-ISIL gunmen occupied parts of Marawi, the main Muslim city in a mainly Catholic country, on May 23 following a foiled attempt by security forces to arrest Hapilon.
The military says Hapilon joined forces with the Maute group to plan the rampage.
Since then more than 1,000 people have been killed and 400,000 residents displaced.
Mr Duterte has imposed martial law across the southern third of the Philippines to quell the militant threat.
The insurgents have withstood a relentless US-backed bombing campaign and intense ground battles with troops that have left large parts of Marawi in ruins.
Defence chiefs last month said other Philippine militant leaders had been killed in the battle for Marawi.
Troops are still pursuing Malaysian Mahmud Ahmad in the Marawi battle zone, Mr Lorenzana said on Monday, describing him as the "conduit" between ISIL and local militant groups.
The mainly Muslim southern Philippines is home to a decades-old separatist insurgency and to extremist groups that have declared allegiance to ISIL, including the Abu Sayyaf and Maute groups.
Hapilon is believed to have been involved in 2001 kidnappings of three Americans, two of whom were later killed.
Hapilon was based in southern island of Basilan but authorities said in January that he had moved to the Mautes' base in Lanao del Sur province, 300 kilometres east, to create an alliance and to establish an ISIL presence there.
Marawi is Lanao del Sur's capital and largest city.
The armed forces chief said the deaths of Hapilon and Maute signalled the end of their militant groups.
"This means their centre of gravity has crumbled," General Eduardo Ano said.
"We just needed to get these two to make sure the leadership, the centre of gravity falls, and elsewhere even the Maute-ISIS in other areas would also crumble."
However an analyst said the killing of the two leaders would probably prompt retaliatory attacks from their followers and allies, with young leaders seeking to take their place.
"Terrorism will take a new form in the post-Marawi period because these terrorist groups linked to ISIS continue to innovate and their actions are evolving," said Rommel Banlaoi, chairman of the Philippine Institute for Peace, Violence and Terrorism Research.
"It's going to be a new battle."