MANILA, Philippines >> A Muslim rebel chief whose forces in the southern Philippines have pledged support to the Islamic State group has died following a long ailment and was replaced by a Middle East-trained militant, the Philippine military and insurgents said Wednesday.

Ameril Umbra Kato, who had backed al-Qaida-linked militants and opposed peace with the Philippine government, died and was buried Tuesday in the south. He was replaced by his deputy Esmail Abubakar as the new leader of the Bangsamoro Islamic Freedom Movement.

Military chief of staff Gen. Gregorio Pio Catapang urged Kato’s estimated 100-150 fighters to rejoin the main Muslim rebel group that signed a peace deal with the government last year, or face a continuing manhunt and assaults.

With Kato’s death and recent battle setbacks, the hard-line insurgent group could now be defeated easier and prevented from launching more bombings and attacks aimed at undermining the government’s peace deal with the 11,000-strong Moro Islamic Liberation Front, Catapang said.

“Hopefully we can decimate their whole organization and prevent them from becoming a spoiler,” Catapang said.

Kato and his forces broke off from the Moro group about four years ago and vowed to continue fighting for a separate Islamic state in the south of the largely Roman Catholic country.

Moro leader Al Haj Murad Ebrahim would write a letter to condole with Kato’s family but would also urge the remaining Bangsamoro fighters to rejoin the main rebel group and benefit from a cease-fire with government forces, Moro rebel Mohagher Iqbal said.

But Kato’s spokesman, Abu Misry, said his group will continue fighting and would never surrender.

“We will never go back to the (Moro group) because it’s no longer waging jihad,” Misry said.

Kato’s successor Abubakar, Misry said, is a Middle East-educated militant in his 40s who has led his men in the battle front lines, including in recent months when government forces launched a major offensive against their group.

Catapang said troops killed more than 150 of Kato’s fighters in that offensive and drove them away from their strongholds in the marshy heartland in the south, where they provided sanctuary to terrorists and made bombs.

Kato’s forces, along with some commanders of the violent Abu Sayyaf extremist group, have publicly expressed support to the Islamic State group but there has been no evidence of actual connections to the Middle East-based extremists, according to military officials.

Kato’s group was implicated in the deaths of 44 police anti-terror commandos, who were killed in clashes with different armed groups in January after gunning down a top Malaysian terror suspect near Mamasapano town.

It’s one of at least four rebel groups outside of a new Muslim autonomy deal the government signed with the Moro Islamic Liberation Front to try to peacefully settle a decades-long rebellion that has left more than 150,000 people dead and undermined progress in the country’s south.