Manila, April 30 -- Malacanang on Wednesday expressed alarm over the arrest of a Chinese national allegedly carrying surveillance equipment near the Commission on Elections' (Comelec) main office in Manila.

Presidential Communications Office Undersecretary and Palace Press Officer Claire Castro said a thorough investigation is needed following the arrest of another Chinese national suspected of engaging in intelligence, surveillance, and reconnaissance operations in the Philippines.

"That is an issue of national security. So, we will just leave it at that. And we will just have an investigation, thorough investigation on that matter," Castro said in a Palace press briefing.

"It's quite alarming and the President has this trust on these...