Philippine marines killed eight suspected sympathizers of the Islamic State (IS) group in a clash in Sultan Kudarat on Thursday, seizing bomb-making equipment, assault rifles and black flags, military officials said.

The bandits were killed in a brief clash at dawn in a hinterland off Palimbang town in Sultan Kudarat province, Brigadier General Emmanuel Salamat said. They were mostly Filipinos but one was possibly Indonesian.

Recovered documents show the slain bandits belonged to Ansar Al-Khilafa Philippines, a new bandit group with about 50 fighters who pledged their allegiance to IS group leader Abu Bakr al-Baghdadi last year.

The hostile Islamist caliphate however does not recognize nor sanction the group.

Marines found two assault rifles, a pistol, bomb-making equipment and materials, two-way radios, documents and five IS group-inspired flags, some of which were displayed at the bandits’ encampment, according to a military report and Salamat.

“Our forces were moving to arrest them but these lawless elements opened fire,” Salamat said by phone. “We have received information that they were conducting bomb-making training and that they may take steps to expand their group, so they became a target of a law enforcement operation.”

It was not immediately clear if the leader of the bandits, Mohamad Jaafar Maguid, who uses the nom de guerre Abu Ghaib or Commander Tokboy, was among those killed, Salamat said.

A government report links Maguid and his men to at least six attacks, including the killing of an Army soldier, two grenade-throwing incidents and a roadside bombing in April 2010 in Sarangani’s Malapatan town.

Muslim bandits from at least three small armed groups in the country’s volatile south, including the Ansar Al-Khilafa and the violent Abu Sayyaf, have pledged support to the IS group leader but there is no evidence they have an active collaboration with the brutal group based in Syria and Iraq, Philippine security officials say.

The Philippine Marine raid on Thursday was coordinated with a larger Muslim rebel group, the Moro Islamic Liberation Front, to prevent its fighters from being accidentally drawn in any fighting. The 11,000-strong Moro rebel group has signed a peace deal with the government and has a presence in Sarangani province, about 1,000 kilometers (600 miles) south of Manila, to prevent a similar incident last January that led the MILF in unwanted friendly fire, killing 44 police commandos in a similar antiterrorism raid.

The MILF and the proposed Bangsamoro Basic Law came under furious criticism as a result of the deaths of the commandos.