Vietnam has denouced a Chinese law that requires foreign vessels to seek approval from Chinese regional authorities to operate in large areas of the disputed East Sea, internationally known as the South China Sea.
Vietnamese Foreign Ministry spokesman Luong Thanh Nghi said in a statement late Friday that the law and other moves by China in recent months are "illegal and invalid" and seriously violate Vietnam's sovereignty over the Hoang Sa (Paracels) and Truong Sa (Spratlys) islands.
"Vietnam demands that China abolish the above said wrongful acts, and practically contribute to the maintenance of peace and stability in the region," he said.
The rules, approved by China's southern Hainan province, took effect on January 1 and compel foreign fishing vessels to obtain approval to enter the waters, which the local government says are under its jurisdiction.
China and four members of the Association of Southeast Asian Nations (ASEAN) - Vietnam, the Philippines, Malaysia and Brunei - are embroiled in sovereignty disputes over the East Sea.
China's claim is the largest, covering most of the sea's 1.7 million square kilometers, a move emphatically rejected by the other claimants and independent experts.
The Philippine Department of Foreign Affairs said in a statement Friday that the new Chinese regulation "escalates tensions, unnecessarily complicates the situation in the South China Sea, and threatens the peace and stability of the region."
Washington also called the fishing rules "provocative and potentially dangerous", prompting a rebuttal from China's foreign ministry on Friday, Reuters said.
Foreign Ministry spokeswoman Hua Chunying said the government "has the right and responsibility to regulate the relevant islands and reefs as well as non-biological resources" according to international and domestic law.
Analysts say at this stage it remains to be seen whether these rules have been approved by the central government.
"We still have to wait and see whether the new rules are affirmed by Beijing and whether they are enforced by Beijing," Sam Bateman, a maritime security researcher at Singapore's Nanyang Technological University, told Thanh Nien News.
But analysts say it is an obligation under the United Nations Convention on the Law of the Sea, to which both Vietnam and China are signatories, for the littoral countries of the East Sea to cooperate in the management of the living resources of the sea.
"The new rules suggest unilateral action by China contrary to the obligation to cooperate," Bateman said.
"If it turns out that these rules have been approved by Beijing, I would expect legal action to challenge the rules."
The East Sea is thought to hold vast untapped reserves of oil and natural gas that could potentially place China, the Philippines, Vietnam, and other claimant nations alongside the likes of Saudi Arabia, Russia, and Qatar.
In 1974, taking advantage of the withdrawal of the American troops from the Vietnam War, China invaded the Paracel Islands. A brief but bloody naval battle with the forces of the then US-backed Republic of Vietnam ensued.
Vietnam's behemoth northern neighbor has illegally occupied the islands ever since. But a post-1975 united Vietnam has never relinquished its ownership of the Paracel Islands and continues to keep military bases and other facilities on the Spratly Islands.