DATU SALIBO, Philippines: The Philippine military said it has teamed up with old foes behind a long-running Muslim insurgency as it looks to eject a breakaway gang of radical militants pledging loyalty to the Islamic State group.

As artillery shells and rockets pounded targets nearby, soldiers were seen mingling freely with several hundred Moro Islamic Liberation Front (MILF) fighters who have joined an assault on gunmen in the restive southern island Mindanao.

In this photo taken on September 5, 2017 shows a Moro Islamic Liberation Front (MILF) rebel (L) with face covered, along with a government soldier (R) manning a mobile check point in Datu Salibo town, Maguindanao province, in southern island of Mindanao. Photo by AFP / FERDINANDH CABRERA

The joint operation is the latest tactic by the Philippine government to try to stamp out pro-IS fighters, after months of battling a separate faction of militants who have besieged the city of Marawi, about 100 kilometers (60 miles) to the north.

Maj. Gen. Arnel dela Vega said militant groups had taken the opportunity “to build up their forces” while government troops were engaged in the Marawi conflict.

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The alliance with MILF included “providing them with indirect fire support and even air support and other expertise.” He said that the awkwardness of fighting alongside former long-time foes had evaporated.

A rebellion by the 10,000-strong MILF has claimed more than 100,000 lives, by government estimates. The group signed a peace treaty in 2014 but will not disarm before the government passes a proposed law granting autonomy to the Muslim regions of the mainly Catholic nation.

But small factions continue to fight, as frustration builds over the bill, which has stalled in Congress.

The military is feeding intelligence to the MILF in the fight against about 60 militants led by Esmael Abdulmalik alias Abu Turaifi, a former MILF guerrilla leader, according to dela Vega.

But he said troop units would not merge with the MILF fighting groups because they had “different operational tactics and procedures.”

“By and large the result has been substantially in our favor,” dela Vega said.

A television journalist saw two military helicopters firing at the militant faction’s positions, while a police van collected MILF dead and wounded near the farming town of Datu Salibo on Tuesday.

Dela Vega said that the deal was a “win-win” situation for both the government and the MILF.

Mohagher Iqbal, a senior MILF leader, said the breakaway Abu Turaifi-led militants wanted to steal the MILF’s guerrilla army and had the same goals as the pro-IS militant faction seeking to carve out territory in Marawi.

The Marawi battle has left nearly a thousand people dead, but several dozen gunmen continue to resist months of air strikes and still hold hostages.