"In the ensuing chase, one of the Vietnamese boats initiated very unsafe maneuvers that resulted in it slamming into the left front and left center of the Philippine patrol vessel", the DFA said in a statement.
Presidential Spokesperson Ernesto Abella noted that the Vietnamese fishing boats "were seen fishing 34 nautical miles off Cape Bolinao in Pangasinan well within exclusive economic zone".
The Foreign Ministry has taken measures to protect Vietnamese citizens in the Philippines after receiving reports that the Philippine coast guard force fired at fishing vessel PY 96173 TS of Phu Yen province, killing two and seizing a number of other fishermen.
The five fishermen in custody would face poaching charges as they were within Philippine waters, he added. "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.
Foreign fishermen have often been caught trespassing in Philippine seas.
That incident triggered a diplomatic spat, with Taiwan suspending the hiring of Philippine workers and recalling its envoy to Manila in protest.
"We would like to offer our sympathies over the unfortunate loss of life", Cayetano told Vietnamese Foreign Minister Pham Binh Minh at a meeting on the sidelines of the United Nations General Assembly in NY.
Covarrubias said the Vietnamese boat rammed the Philippine Navy patrol ship. he said he could not yet say what caused the death of the two fishermen and if shots were fired during the arrests, saying an investigation is underway to look deeper into the incident.