Vietnamese boat has sunk after it collided with a Chinese vessel near a controversial oil rig in the South China Sea, amid tensions between the two nations.
Both countries are blaming the other for the incident.
Vietnam's coast guard said the boat was encircled by 40 Chinese vessels before it was rammed, reports said.
But Chinese state media outlet Xinhua said Vietnam's boat collided with its vessel after 'engaging in harassment'.
The BBC's Martin Patience says that whatever the truth, the sinking is likely to further escalate tensions between the two countries, given that for the past few weeks they have engaged in skirmishes at sea.
The two are locked in an intensifying dispute over South China Sea territory.
Vietnam has protested against China moving its Haiyang Shiyou 981 rig to waters also claimed by Hanoi, at a spot near the disputed Paracel Islands.
Tuesday's incident happened just 17 nautical miles from the rig, Vietnamese reports said.
Xinhua on Tuesday claimed that Vietnam had 'on many occasions dispatched various boats with the sole intention of harassing Chinese-linked companies drilling in that part of the ocean'.
It said China had made serious representations to Vietnam to request that it 'halt its harassing and destructive activities'.
Vietnamese media meanwhile reported that China deployed 'a fast attack missile boat and a minesweeper&qu.