Beijing said Chinese fishing boats were chased away by armed Vietnamese ships in the incident on Thursday.


One of the Chinese boats became tangled with the cables of a Vietnamese oil exploring vessel, which continued to drag the Chinese vessel for more than an hour before the net had to be cut, the foreign ministry said.


China accused Vietnam of "gravely violating" its sovereignty, saying Vietnam's actions had endangered Chinese sailors' lives, and warned it to stop "all invasive activities".


'Premeditated'


Beijing's strong-worded statement followed Vietnam's accusation that a Chinese fishing boat had "intentionally rammed" the exploration cables of a Vietnamese boat - the second such incident in two weeks.


Vietnam said the "premeditated and carefully calculated" attack was part of China's attempts to control disputed waters.


Vietnam now says it will stage live ammunition drills on Monday in an area off central Quang Nam province.


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The announcement was made on Friday on the website of the state-owned Northern Maritime Safety Co-operation, warning all vessels to avoid the area.
 
It said the decision to hold the exercises was taken on 7 June.
 
China is engaged in maritime border disputes with several countries.
 
The South China Sea includes important shipping routes and may contain rich oil and gas deposits.
 
The Philippines, Malaysia, Brunei and Taiwan also have rival claims in the area. The US has also expressed concern about China's rising naval ambitions.

Vietnam plans live-fire drill amid South China Sea row