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Hanoi Vietnam’s government claims that a Chinese vessel rammed and sank a Vietnamese fishing boat in disputed waters in the South China Sea.

The fishing boat was around 370 kilometres off Da Nang near Discovery Reef in the Paracel island chain on Wednesday when it was rammed by a Chinese vessel, the National Committee for Incident, Natural Disaster Response and Search and Rescue said in a statement.

The five Vietnamese men on board the fishing boat clung on to the sinking bow until they were rescued, the statement said.

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Vietnam’s government and state media have previously accused Chinese vessels of attacking Vietnamese fishing boats.

In April and May, more than 10 Vietnamese fishing boats were allegedly hit and robbed while fishing in the South China Sea, according to Vietnam’s Tuoi Tre newspaper.

China claims almost all of the South China Sea, including waters internationally recognised as Vietnam’s exclusive economic zone where Vietnam has sole fishing rights.

Greg Poling, a fellow with the Southeast Asia Program at the Center for Strategic and International Studies, slammed China over the incident.

“A Chinese ship reportedly rams and sinks a Vietnamese fishing boat in the Paracels (again),” he said on Twitter.

“China’s neighbors have become so numb to the constant exercise of low-intensity violence and intimidation that it will warrant barely a mention in regional press.”

Chinese ship reportedly rams and sinks a Vietnamese fishing boat in the Paracels (again). China's neighbors have become so numb to the constant exercise of low-intensity violence and intimidation that it will warrant barely a mention in regional press. https://t.co/fgumeS3MXR — Greg Poling (@GregPoling) March 7, 2019

The incident came as Vietnam jailed 15 people for “causing public disorder” during anti-China protests.

Scores have been jailed in the wake of rare nationwide demonstrations in June 2018 that quickly turned violent in some areas as police struggled to quell the unrest.

On Thursday, 15 people were sentenced to between two and 3.5 years in jail by a court in southern Binh Thuan province, where police stations were ransacked and security vehicles destroyed.

State-run Vietnam News Agency said “the 15 defendants were shouting, instigating the crowd” and blocked traffic on a major highway for 15 hours, citing the official indictment.

“The jury board concluded that the defendants’ behaviour undermined security, order and social safety... so they need to be seriously punished,” VNA reported.

A court official confirmed the sentences and said several others are currently under investigation on similar charges, he told AFP, refusing to be named.

Last year’s unrest was sparked by a proposal by the government to establish several economic zones with 99-year leases in the country that protesters said were designed to cater to Chinese investors.

The draft bill made no mention of China - and the government backed off the lengthy lease terms - but it was not enough to prevent the demonstrations in several cities, including Hanoi and the southern commercial hub of Ho Chi Minh City.

The bill has been shelved for now and officials have not said whether it may be revived.

The investment zones were aimed at attracting foreign cash to the fast-growing, export-oriented economy.

The one-party state has clocked glittering growth in the past decade, while maintaining a firm grip on power.