Hanoi: Vietnam has accused Beijing of violating its sovereignty with a scientific survey in waters around two disputed island chains in the South China Sea, the Foreign Ministry said.

Hanoi called on China to immediately cease and refrain from further such acts.

Tensions are already running high between the neighbours -- which both claim the potentially oil-rich Paracel and Spratly archipelagos -- and Hanoi has seen several anti-China rallies in the past few months.

The statement referred to a report carried by China's state news agency said that a research vessel, Tan Bao Hao, had conducted a scientific survey in the sea between the two island groups.

"The Vietnamese Foreign Ministry's representatives met the Chinese side and stated Vietnam's points of view, lodging Vietnam's protest against China's acts, which violate the sovereignty and jurisdictional rights of Vietnam," ministry spokeswoman Nguyen Phuong Nga said.

China and Vietnam have a long-running dispute over the island groups, which straddle vital commercial shipping lanes.
Tensions flared in May when Vietnam accused Chinese marine surveillance vessels of cutting the exploration cables of a Vietnamese oil survey ship inside Vietnam's waters.

Hanoi has seen nine anti-China rallies in 10 weeks – an unprecedented run of street action in communist Vietnam, where overtly political demonstrations are rare.

Authorities in the city allowed the most recent protests to go ahead, including one on Sunday, but have forcibly dispersed two previous demonstrations following talks between Hanoi and Beijing in June.