MANILA, Philippines (AP) — Philippine troops killed nine suspected Muslim militants in the volatile south, including two key suspects in a bomb attack last month that left four Christian worshippers dead, the army said Saturday.

Four army scout rangers were slightly wounded in Thursday’s operation against the Dawlah Islamiyah, a small outfit aligned with the Islamic State group, in the hinterland village of Taporug near Piagapo town in Lanao del Sur province, army spokesman Col. Louie Dema-ala said.

Army forces clashed with about 15 militants in a series of shootouts from Thursday to Friday after some villagers tipped off the military of their presence, Dema-ala, adding that the surviving militants escaped and were being pursued.

Maj. Gen. Gabriel Viray III, an army infantry division commander, said the militants retreated from fierce exchanges of fire until they were trapped in a rural house, where they tried to fight back before being taken down.

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“We call upon the community to remain vigilant and collaborate with the army and government authorities as we collectively work towards eliminating the threat posed by local terrorist groups,” the army said in a statement.

Eight of the nine bodies had been identified, including those of Saumay Saiden and Abdul Hadi, who were among the suspects in the Dec. 3 bombing that killed four Christian worshippers and wounded dozens of others during Sunday Mass in a state-run university gymnasium in southern Marawi city, he added.

Hadi allegedly assembled the bomb, which police investigators said consisted of a 60 mm mortar round and a rifle grenade, Dema-ala told reporters.

A post-battle video, which a government intelligence official showed The Associated Press, conveyed nine bodies lying side by side near a huddle of rural huts surrounded by banana trees as army officers examined each.

Military chief of staff, Gen. Romeo Brawner, said “this operation sets a clear precedent: the Armed Forces of the Philippines will not tolerate those who endanger the lives and well-being of our people.”

“The remaining few will face our full force and unshakeable resolve in bringing every single responsible individual to account,” Brawner said.

The southern Philippine region of Mindanao is the homeland of minority Muslims and has been the scene of decades-old separatist rebellions.

The Marawi city bombing in December was the bloodiest insurgency-related violence so far under President Ferdinand Marcos Jr. He blamed “foreign terrorists” for the attack, which set off a security alarm, including in the capital, Manila. Government forces were put on high alert at the time, as the largely Roman Catholic country welcomed the busy Christmas season that marks a festive period of travel, shopping sprees and traffic jams.

The largest armed insurgent group, the Moro Islamic Liberation Front, signed a 2014 peace deal with the government, considerably easing decades of fighting. But smaller armed groups like the Dawlah Islamiyah rejected the peace pact and have struggled to press on with bombings and other attacks while evading government offensives.