MANILA, Philippines - The Navy spotted two Chinese ships intruding in Philippine-owned Ayungin Shoal last Saturday.

Col. Edgard Arevalo, Navy spokesman on West Philippine Sea issues, over the weekend said a Chinese maritime surveillance vessel joined another ship spotted on Friday night.

â€œVessels come and go and we cannot be sure if they are out there permanently,â€ he said.

â€œWhile we are not sure about that, you can be sure that we are vigilant. Our personnel there (in Ayungin Shoal) serve as our eyes and ears in that isolated post who render round-the-clock reports and record what they observe as those form part of the documents required as basis for the governmentâ€™s legal recourse and resort to arbitration.â€

Ayungin Shoal is 105.77 nautical miles from Palawan and forms part of the Philippinesâ€™ 200- nautical mile exclusive economic zone.

It is part of the Kalayaan Island Group off Palawan and the subject of a territorial row.

On May 10, the Philippines filed a protest against China for illegal deployment of vessels around the shoal.

The protest decried the provocative presence of two CMS and one warship in violation of international law.

The Philippines has also asked China to respect its sovereign rights and jurisdiction over its continental shelf.

China claims virtually the entire West Philippine Sea while the Philippines, Malaysia, Vietnam, Brunei and Taiwan have overlapping claims.

The Philippines described Chinaâ€™s claim as â€œexcessive.â€

Early this month, a Chinese warship harassed a utility boat of Kalayaan Island town with 147 civilians on board, included the group of Mayor Eugenio Bito-onon.

Bito-onon said the Chinese warship used powerful floodlights and sailed toward their boat several times, coming as close as 50 meters.