Malacanang admitted on Thursday that authorities' confirmation of having first Filipino suicide bomber is a cause for concern.

In a press briefing, Presidential Spokesperson Salvador Panelo said President Rodrigo Duterte has ordered security forces to strengthen surveillance and intelligence gathering against terrorists.

"It’s a cause for concern, given that this is the first time that there is a Filipino suicide bomber. It goes against the grain of the character of Filipinos, which is committing suicide for terrorism," he said.

The police and military have said one of the two attackers in the twin blasts in Indanan, Sulu late last month was a Filipino, the first officially confirmed case.

Eight people, including the two attackers and three soldiers, were killed and several others were injured in the explosions.

Asked of Duterte's directive to the security agencies, Panelo said, "The directive is always to enhance the technology in surveillance and intelligence work."

The attacks came despite the existence of martial law in Mindanao.

Panelo, also the chief presidential legal counsel, said it would be up to Duterte if he would prolong martial rule in the southern Philippines, which expires on December 31, 2019. Celerina Monte/DMS