MALACANANG promised on Monday a "fair and thorough" investigation into a sea chase incident which led to the death of two Vietnamese fishermen on Saturday.
The Bolinao police said in a report that the Vietnamese boat was one of six that had been spotted in the area, allegedly violating worldwide law by fishing in the Philippines's so-called exclusive economic zone.
Filipino Foreign Secretary Alan Peter Cayetano informed his Vietnamese counterpart, Pham Binh Minh, of the encounter during a meeting at the United Nations in NY on Sunday, assuring him of a "fair and thorough investigation", the Associated Press reported.
The secretary offered the assurance at an informal meeting of ASEAN foreign ministers, the ministry said.
The Philippine foreign affairs department said navy personnel had fired warning shots after the Vietnamese vessel had initiated "very unsafe manoeuvres". There were six bullet holes in the boat, the report said, and the Vietnamese were later determined to have died from gunshot wounds.
Teams from the Philippine Navy, the coast guard and the national police are investigating.
The Navy vessel was enroute to Subic, Zambales when the Filipino officers spotted six Vietnamese fishing vessels inside the 200-nautical-mile Philippine exclusive economic zone.
The DFA said those who were arrested "will be accorded proper treatment" and "can be accessed anytime" by Vietnamese embassy officials.
"The reports said this prompted personnel on board the Navy vessel to fire warning shots and when the Navy personnel boarded the fishing vessel, they found two dead Vietnamese fishermen. While it was chasing the boats, one boat manoeuvred and hit our vessel", said Covarrubias.
Immediately after receiving the report, the ministry instructed the Vietnamese Embassy in the Philippines to contact the departments of Foreign Affairs and National Defence of the Philippines to verify the information and take appropriate measures to protect the citizens.
The Filipino navy personnel "followed the rules of engagement, including identification protocol and use of radio and public address system", the official said, adding that the Vietnamese fishing boat was towed to Pangasinan after the incident.
The Philippines assured Vietnam the detained fishermen would be well treated.