Philippine authorities have arrested seven Vietnamese fishermen for allegedly poaching and illegal fishing within the country's exclusive economic zone in the South China Sea, the military said on Sunday.

Lieutenant Colonel Isagani Nato, chief public information officer of the Armed Forces of the Philippines' Northern Luzon Command, however, could not confirm reports that two of the seven fishermen died.

"It's (apprehension) under investigation," he said in a phone interview.

He said that a body was formed to conduct the joint investigation into the incident. The body is composed of the Pangasinan Provincial Police Office, Bolinao Municipal Police Office, Criminal Investigation and Detection Group, Philippine Coast Guard and Philippine Navy.

Nato said an investigating body was formed due to the implication on the diplomatic relations with Vietnam with the apprehension of its nationals.

According to Nato, the Vietnamese fishermen were arrested about 23 nautical miles of Bolinao Point off Pangasinan at around 10am on Saturday by the Philippine Navy.

As of Sunday morning, he said the arrested fishermen were still off Bolinao.

The South China Sea has been claimed wholly or partially by the Philippines, Vietnam, Brunei, Malaysia, China and Taiwan. Celerina Monte/DMS