Sulu Sultan Jamalul Kiram III and his men who staged a standoff against Malaysian authorities in Sabah will face charges, Justice Secretary Leila De Lima said Thursday.
The National Bureau of Investigation is in the process of building a "airtight cases" against Kiram and his men, the Secretary added.
Her statement came at the heels of Kiram's calls for a unilateral ceasefire in Sabah, which was rejected by the Malaysian government.
Clashes have raged in the Borneo territory since March 1 after Malaysia launched an all-out offensive against armed Filipinos holed out in Lahad Datu.
Malaysia officials have broached the possibility of asking the Philippines to "extradite" Kiram.
"Ang priority, siyempre, yung pagsasampa ng kaso dito sa Pilipinas (Filing of cases in the Philippines is of course the priority)," reports quoted De Lima as saying.
She added that the NBI is focusing on identifying the appropriate charges, noting that evidence have been collected.
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Earlier reports have floated the possibility of Kiram being charged with inciting to war or giving motives for reprisals, illegal possession of firearms, violations of the election gun ban, and illegal assembly, among others.
Kiram may also face Malaysian laws, De Lima explained.
"I suppose they violated also Malaysian laws," the Justice chief said.
She added they will also look into possible mechanisms of sending Kiram to Malaysia but stressed that the Philippines has no extradition treaty with the neighboring country.
Related story: Kiram camp calls for unilateral ceasefire, Malaysia rejects