A Chinese vessel and two Vietnamese ships collided in water around the Xisha Islands where a Chinese company has deployed an oil rig, Vietnam said on Wednesday.

The foreign ministry in Hanoi said the collisions took place on Sunday and caused considerable damage to the Vietnamese ships. Six people sustained minor injuries, it said.

The China Maritime Safety Administration issued a navigational warning Saturday advising that Hai Yang Shi You 981, a China National Offshore Oil Corporation (CNOOC) owned drilling rig, would be operating from Friday to August 15, in a area south of Zhongjian Island in the Xisha Islands, which Vietnam claims as their own.

Vietnam deployed patrol vessels after the notice.

China's operation of its drilling rig 981 is legal, foreign ministry spokeswoman Hua Chunying said Wednesday at a regular press briefing.

She also urged Vietnam to stop disturbing China's exploration activities in its territorial waters.

Hua said operation of the drilling rig is lawful in China's territorial waters.

She said Vietnamese harassment of Chinese companies conducting normal activities runs counter to international law and basic norms of international relations as well as China's sovereignty and administration rights.

China's State Councilor Yang Jiechi had a phone conversation with Vietnam's Deputy Prime Minister and Foreign Minister Pham Binh Minh on Tuesday, demanding that the Vietnamese side stop disturbing Chinese companies' normal work in the Xisha Islands.

According to Vietnamese officials, dozens of navy and coast guard vessels from both countries are in the area where China has deployed the giant rig. Hanoi has strongly condemned the operation of the drilling rig in what it says are its waters in the South China Sea, and told CNOOC to remove it.

The United States on Tuesday said China's decision to move a deep-sea oil rig into disputed waters in the South China Sea was a "provocative" step which it was monitoring closely.

"We're looking carefully into this matter," State Department deputy spokeswoman Jen Psaki told reporters.

Hua said the Xisha Islands are part of China's inherent territory and the activities of the Chinese companies in the Xisha Islands are within the mandate of China's sovereignty and administration, which have nothing to do with Vietnam and the US.

The United States is in no position to make irresponsible remarks on China's affairs, Hua added.

Agencies - Global Times