The South China Sea has proven oil reserves of around 7.7 billion barrels, with estimates reaching to 28 billion barrels.
Aside from China, the disputed waters are claimed in whole or in part by Vietnam, the Philippines, Taiwan, Brunei and Malaysia.
Tensions escalated in June between China and Vietnam over the Spratly and Paracel Islands, with Vietnam claiming that Chinese vessels cut cables to its oil exploration ships in the contested waters. There have also been standoffs this year between Chinese and Philippine vessels.
And in late July, a Chinese warship confronted an Indian navy ship shortly after it left port in Vietnam. Indian officials said the vessel was still within Vietnam's economic zone.
"I would like to reaffirm that China enjoys indisputable sovereignty over the South China Sea and the island. China's stand is based on historical facts and international law," Chinese Foreign Ministry spokeswoman Jiang Yu told reporters.
While not directly referring to India, Jiang's comment came in response to a question on reports that India's Oil and Natural Gas Corp. Videsh Limited was considering exploration projects in two blocks that Vietnam claims.
The proposed projects are expected to figure in scheduled talks Friday between Indian and Vietnamese external affairs ministers.
"We hope foreign countries will not get involved in the dispute," Jiang said, alluding to India's interest in the blocks. "For countries outside the region, we hope they will respect and support countries in the region to solve this dispute through bilateral channels."
While Vietnam maintains it holds rights to the two blocks under the U.N. Convention on the Law of the Sea, Jiang said the agreement "did not give any country the right to expand their own exclusive economic zone and continental shelf to other countries' territories."
Instead, she said, the convention didn't negate "a country's right formed in history that has been consistently claimed."
Chinese state-run news agency Xinhua reported last week that China and Vietnam had agreed to push ahead with negotiations over the dispute, with the aim of signing a formal agreement.
As for oil and gas exploration activities, our consistent position is that we are opposed to any country engaged in oil and gas exploration and development activities in waters under China's jurisdiction," Jiang said.