MARAWI: The head of the Islamic State group in Southeast Asia, who figures on the US "most wanted terrorists" list, was killed on Monday in the battle to reclaim a militant-held Philippines city, officials said, reports AFP.

Isnilon Hapilon's reported death came during a final push to end the nearly five-month siege of Marawi, a battle that has claimed more than 1,000 lives and raised fears that IS was seeking to set up a regional base in the southern Philippines.

President Rodrigo Duterte and security analysts say Hapilon has been a key figure in the jihadist outfit's drive to establish a Southeast Asian caliphate as they suffer battlefield defeats in Iraq and Syria.

The military said the long-haired leader was killed in a dawn offensive alongside Omarkhayam Maute, one of two brothers who allied with Hapilon to plot the takeover of the city.

"It's a big deal for us that they were killed," Defence Secretary Delfin Lorenzana told reporters, adding that Hapilon's death was a symbolic blow to regional militancy because he had been declared the local emir of the Islamic State group.