Vietnam's foreign ministry has said its oil exploration in the South China Sea, known locally as the East Sea, is a normal practice under a deal with a Spanish partner.
"All relevant petroleum activities by Vietnam take place in waters entirely under the sovereignty and jurisdiction of Vietnam," foreign ministry spokeswoman Le Thi Thu Hang told the press following reports China threatened to attack Vietnamese bases in the East Sea unless Vietnam stopped the drilling project.
The Spanish Repsol Group is in charge of the process and progress of the drilling project, in accordance with the terms agreed by related parties, Hang added.
China claims almost 90 percent of the potentially energy rich ocean, despite competing claims from Vietnam, the Philippines, Brunei, Malaysia and Taiwan. The waters are thought to hold vast untapped reserves of oil and natural gas that could potentially place those who control of them in league with the likes of Saudi Arabia, Russia and Qatar.
China has been ramping up a number of land reclamation projects in the Spratly Islands, a move that has pitted it against Vietnam and the Philippines. Despite a raft of diplomatic protests, including an international lawsuit brought by the Philippines, China has forged ahead with its island-building plans.