Beijing has announced the successful conclusion of an oil rig's exploratory drilling at a site in the South China Sea that has witnessed more than 1,500 incidents of Vietnam sending ships to harass operations.

Experts said China should continue with its lawful maritime oil and gas development as planned and not be intimidated by moves taken and orchestrated by Hanoi and Washington.

Beijing has announced the successful conclusion of an oil rig's exploratory drilling at a site in the South China Sea that has witnessed more than 1,500 incidents of Vietnam sending ships to harass operations.

Experts said China should continue with its lawful maritime oil and gas development as planned and not be intimidated by moves taken and orchestrated by Hanoi and Washington.

Oil drilling platform HYSY981, operated and managed by China Oilfield Services Limited, completed the exploration and drilling operation in the sea near Zhongjian Island, part of China's Xisha Islands, on Tuesday, Foreign Ministry spokesman Hong Lei confirmed on Wednesday.

The company said in a news release that the rig will be "mobilized as scheduled" to the Lingshui blocks, off Hainan, for further operations.

Although it recognized China's sovereignty over the islands 40 years ago in official statements and even in textbooks for high school students, Vietnam has reacted violently since drilling operations started on May 2, heightening tension in the region.

"China firmly opposes provocations by Vietnam against the Chinese enterprise's operations, and has taken necessary measures to ensure safety of operations," Hong said.

The drilling site is "purely within the scope of China's territorial sovereignty and jurisdiction", the spokesman said.

Wang Zhen, a senior expert on geology and an academic at the China Engineering Academy, told Xinhua that the rig was located in a deep water area and since typhoon season is coming it was a prudent decision to move it.

Wu Shicun, president of the National Institute for South China Sea Studies, said Vietnam has harvested lucrative profits in recent years by unilaterally snatching oil and gas from the sea while requiring China to refrain from taking any moves that "heighten tension".

Li Jinming, a professor of maritime law and South China Sea studies at Xiamen University, said the latest maritime action against China by Vietnam, the Philippines and the United States may "seem inflammatory and mind-boggling", but actually "there is a huge lack of confidence behind them".

Through Vietnam involving petroleum giants from the West in joint maritime development, "some powerful regional outsiders have increased their engagement in the South China Sea, which has led to multiple parties acting against China", Wu said.