China defended on Friday its new fishing restrictions in disputed waters in the South China Sea against criticism from the United States, saying the rules were in accordance with international law.

The rules, approved by China's southern Hainan province, took effect on January 1 and require foreign fishing vessels to obtain approval to enter the waters, which the local government says are under its jurisdiction.

Beijing claims almost the entire oil- and gas-rich South China Sea and rejects rival claims to parts of it from the Philippines, Taiwan, Malaysia, Brunei and Vietnam.

Washington called the fishing rules "provocative and potentially dangerous," prompting a rebuttal from China's foreign ministry on Friday.

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.

"For more than 30 years, China's relevant fisheries laws and regulations have been consistently implemented in a normal way, and have never caused any tension," Hua said at a daily news briefing.

"If someone feels the need to say that technical amendments to local fisheries regulations implemented many years ago will cause tensions in the region and pose a threat to regional stability, then I can only say that if this does not stem from a lack of basic common sense, then it must be due to an ulterior motive."

A government-affiliated fishing organization in Vietnam criticized the new rules and the Philippines said they escalate tensions in the region.

"These regulations seriously violate the freedom of navigation and the right to fish of all states in the high seas," foreign ministry spokesman Raul Hernandez said.

"We have requested China to immediately clarify the new fisheries law."

ANOTHER IRRITANT

After China's announcement late last year of an air defense identification zone in the East China Sea, which drew sharp criticism from Washington, the fishing rules add another irritant to Sino-U.S. ties.

"China has not offered any explanation or basis under international law for these extensive maritime claims," State Department spokeswoman Jen Psaki told a news briefing on Thursday.

"Our long-standing position has been that all concerned parties should avoid any unilateral action that raises tensions and undermines the prospects for a diplomatic or other peaceful resolution of differences."

Fishermen from Vietnam and the Philippines have been caught up in heated territorial disputes with China on the seas in recent years. Last year, Vietnam accused China of opening fire on a fishing boat in the South China Sea, and later of endangering the lives of fishermen after ramming a fishing trawler.

The State Department spokeswoman gave no indication of any possible U.S. response to the fishing zone.

STRATEGIC

Hainan officials were not immediately available to comment. But according to the Hainan legislature's website, foreign fishing vessels need approval to enter from the "relevant and responsible department" of the Chinese government's Cabinet.

Hainan, which juts into the South China Sea from China's southern tip, is responsible for administering the country's extensive claims to the myriad islets and atolls in the sea.

It says it governs 2 million square km (770,000 square miles) of water, according to local government data issued in 2011. The South China Sea is an estimated 3.5 million square km (1.4 million square miles) in size.

The province is also home to Chinese naval facilities that include a purpose-built dock for the country's only aircraft carrier and a base for attack submarines.

The fishing rules do not outline penalties, but the requirements are similar to a 2004 national law that says boats entering Chinese territory without permission can have their catch and fishing equipment seized and face fines of up to 500,000 yuan ($82,600).

Wu Shicun, head of Hainan's foreign affairs office until last May, told Reuters that offending foreign fishing vessels would be expelled if they are in waters around Hainan and the disputed Paracel Islands.

"If we can't expel them, then we'll go on board to make checks to see whether there's any illegal fishing," said Wu, now president of the National Institute for South China Sea Studies, a think-tank that advises the government on policy on the South China Sea. "We'll drag you back to be handled, confiscate (your) fishing gear, detain the vessel and fine (you). The most serious fine is 500,000 yuan."

Vietnam reiterated its claim to sovereignty over the Paracel and Spratlys islands in the South China Sea, both also claimed by Beijing.

"All foreign activities at these areas without Vietnam's acceptance are illegal and groundless," Foreign Ministry spokesman Luong Thanh Nghi said in a written response to questions about the new fishing rules.

The government-affiliated fishing organization, the Vietnam Fisheries Society, condemned the Hainan regulations.

"This action from China will directly affect Vietnamese fishermen, damage their work, their livelihoods and impact their families," said Vo Van Trac, vice chairman of the body.

Donald Rothwell, a maritime law expert at the Australian National University College of Law, said the fisheries rules were unlikely to advance China's claims on the South China Sea given the likely reaction from other countries with rival claims.

"The only way it can advance its position is if China actually seeks to enforce these laws and the enforcement mechanisms are successful and prosecutions result or it has conditions found in its favor by international courts," he said.