Chinese and Vietnamese coast guard ships are patrolling near the Haiyang Shiyou oil rig. Photo: AFP
A Vietnamese fishing boat has sunk after it collided with a Chinese vessel near a controversial oil rig in the South China Sea, further escalating the tensions between the two nations.
Both countries are blaming the other for the incident, BBC reported.
Vietnam's coast guard said the boat was encircled by 40 Chinese vessels before it was rammed, reports said.
But Chinese state media Xinhua said Vietnam's boat capsized after harassing and colliding with a Chinese fishing boat around 5 pm Monday.
Crew aboard the boat were saved after Vietnam boat jostled the fishing boat from Dongfang City in southern China's Hainan Province and overturned in the waters near China's Xisha Islands, Xinhua reported.
The two nations are locked in an intensifying oil rig dispute in the South China Sea.
Vietnam has protested against China moving its Haiyang Shiyou 981 rig to waters also claimed by Hanoi.
The incident happened just 17 nautical miles from the rig, which is 240 km (150 miles) off Vietnam's coast and 330 km (206 miles) from the southern coast of China's Hainan island.
Vietnam has sent a number of ships to obstruct the drilling of Chinese companies in the waters where the collision took place. The Chinese side has taken measures to stop Vietnamese interference and lodged serious representations to the Vietnamese side, asking them to immediately stop the disruptive activities, according to Xinhua.
China's refusal to move the rig sparked anti-China protests in Vietnam earlier in May, which left at least four people dead and several factories burnt.
China in recent days has upped its rhetoric on the South China Sea.
On Monday, a spokesman for China's foreign ministry addressed a recent attempt by Vietnam to list its historical claims to the Xisha Islands, saying it was "absurd and laughable".
On the same day, Xinhua published a commentary in English which accused Vietnam of wanting to "disturb and play up the normal drilling of Haiyang Shiyou 981".
Written by Chinese law professor Yang Zewei, the commentary states: "Hanoi should know that such drilling in the said area is China's sovereign right endowed by the United Nations Convention on the Law of the Sea."
"Vietnam should immediately stop any interruptive activities and undertake corresponding consequences and international responsibilities for its provocations.".