Vietnam, accusing China, told Reuters on Sunday that its navy would do everything necessary to protect its territorial integrity after three Chinese patrol boats confronted and damaged an oil investigation ship operated by PetroVietnam, the state-owned oil and Gas Company.

China’s claim of Vietnamese ship conducting a seismic survey in Chinese water was rejected by Vietnamese officials in a weekend news conference. The incident took place about 120 km (80 miles) off the south-central coast of Vietnam and some 600 km (370 miles) south of China's Hainan Island, Vietnamese officials said.

The Vietnamese navy will do everything that is necessary to protect peace, independence and territorial integrity of Vietnam, foreign ministry spokeswoman Nguyen Phuong Nga said.

“One of the Chinese patrol vessels intentionally cut a submerged cable tow by the ship, the Binh Minh 02, it is not the first time they are cutting cables of Vietnamese boats, Do Van Hau, deputy chief executive of state oil and gas group PetroVietnam said.

The South China Sea covers an important shipping route. China, Vietnam, the Philippines, Malaysia, Brunei and Taiwan all claim territories in the sea.

The fact that China is trying to find ways to realize (its territorial claims) is clearly increasing the tension in the region, Nguyen Duy Chien, vice chairman of the Vietnamese foreign ministry's national boundary commission told Reuters.

China also blamed Vietnam on Saturday, saying such Vietnamese oil and gas operations damaged China's interests and jurisdictional rights.

Chinese Foreign Ministry spokeswoman Jiang Yu said the behaviour of the China” in the incident was normal.