Vietnam has accused a Chinese vessel of sinking a Vietnamese fishing boat in the South China Sea, increasing tensions between the two countries over rival territorial claims to the waters.
The incident on Monday happened 30kms southwest of a large oil rig deployed by China in early May in a disputed area of the sea.
A representative of the Vietnamese fishing industry, Tran Van Linh, said 40 Chinese boats had surrounded a group of vessels, ramming and sinking one of them.
He said the people on board were picked up by other Vietnamese boats and that there were no injuries.
Linh called the alleged attack a "perverse, brutal and inhumane action" by the Chinese, the AP news agency reported.
The allegations have been denied by China, which put the blame on the Vietnamese side.
The state-run Xinhua news agency said the Vietnamese vessel was "harassing" the Chinese fishing boat it collided with.
"The crew aboard the boat were saved after their ship jostled a fishing boat from Dongfang City in southern China's Hainan province," government sources told the news outlet.
According to Xinhua, China's government had begun talks with Vietnam over the incident, the Reuters news agency reported.
The oil rig deployed by China angered Vietnam and set off violent anti-China riots that led to an evacuation of Chinese citizens from Vietnam.
Vietnam has sent patrol ships to confront the rig, and China has deployed dozens of ships to protect it.
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The two countries, which have close economic ties, have been involved in a tense standoff, occasionally colliding with each other.
The neighbours have long argued over the sovereignty of the South China Sea, spurred on by the oil and natural gas deposits the waters contain.
However, despite the history of dispute, Linh said it was the first time China had sunk a Vietnamese boat.
China claims nearly all of the South China Sea as its own, bringing it into conflict with the far smaller nations of Vietnam, the Philippines and three others that have rival claims.
In recent years it has been more assertive in pressing its claims in the waters and resisting attempts to negotiate.
The US, which shares the concerns of the smaller claimant states about China's rising military might, called China's deployment of the rig "provocative".
Vietnam is trying to rally regional and international support against Beijing, but its options are limited because China is the country's largest trading partner.