Chinese patrol ships arrested six Vietnamese fishermen in waters off Hainan Island, officials said yesterday, an incident likely to heighten tensions between the nations as they spar over a territorial dispute.
The two nations yesterday disputed just where Thursday's incident took place.
Chinese Foreign Ministry spokesman Hong Lei said the arrests occurred 12km off Hainan, a location that would place the fisherman within China's territorial waters.
However, Nguyen Ky, a Vietnamese official in the district where the fishermen came from, said the arrests took place in disputed waters near the Gulf of Tonkin, which lies off Hainan.
He said his information came from fishermen in a second boat that was detained and reported the incident via radio. Vietnam's state-run Tuoi Tre newspaper said the men were detained in "common fishing grounds" in the Gulf of Tonkin.
Hong said Chinese authorities were investigating the situation "in accordance with the law" and urged Vietnam to "strengthen control over their fishermen .... and prevent similar incidents from happening again".
Vietnam's Ministry of Foreign Affairs did not immediately return calls seeking comment. Analysts said the arrests would fuel tension between the two nations.
"This poisons the atmosphere further," Carlyle Thayer, an emeritus professor at the Australian Defence Force Academy in Canberra, said.
"It's a unilateral act in an area where Vietnam has clear authority or it is in dispute.
"It will add more pressure on the Vietnam government" to respond.
Vietnamese fishermen have been detained by China before, but this is the first time since China deployed a large oil rig in early May close to the disputed Paracel Islands, which China calls the Xisha Islands, and Vietnam calls the Hoang Sa Islands.
Its deployment caused a dangerous rise in tensions between the two nations, with Hanoi sending coastal patrol ships to try to force away the rig, which is protected by a large flotilla of Chinese ships.
The Vietnamese ships have been unable to get close to the rig, and dozens have been damaged in collisions with larger Chinese vessels, said Vietnamese officials.
Tensions over the oil rig also sparked violent anti-Chinese riots in Vietnam in May.
Beijing said four Chinese citizens died in the unrest, while Vietnam put the toll at three.
Vietnamese foreign ministry spokesman Le Hai Binh said on Thursday that Hanoi was "carefully considering" possible legal action against Beijing over the rigs deployment.
China claims nearly all of the South China Sea and has become increasingly assertive in staking its claim.
Vietnam yesterday revealed plans to spend US$540 million to build 32 coastal patrol vessels to boost its maritime muscle and surveillance capacities.
Additional reporting by Agence France-Presse, Bloomberg