(Adds U.S. ambassador's comments, paragraphs 2, 12-13)
By John Ruwitch and Michael Martina
SHANGHAI/BEIJING, Dec 5 (Reuters) - New Chinese regulations allowing police to board vessels deemed to be breaking the law off the southern island of Hainan were a provincial-level initiative, but Beijing likely signed off on them, an official said on Wednesday.
China is in an increasingly angry dispute with neighbours including the Philippines, Taiwan, Vietnam, Brunei and Malaysia over claims to parts of the potentially oil and gas-rich South China Sea and U.S. Ambassador Gary Locke said the United States was seeking clarification on the new rules.
China lays claim to almost the whole of the sea, which is criss-crossed by crucial shipping lanes.
The rules passed last week by Hainan island's provincial legislature were partly a response to an increase in Vietnamese fishing boats near the Paracel islands, which both countries claim, said Wu Shicun, head of Hainan's foreign affairs office.
Vietnam on Tuesday condemned China's claims as a serious violation of its sovereignty, and planned to set up patrols to protect its fisheries, accusing Chinese boats of sabotage.
Wu, who also heads the National Institute for South China Sea Studies, said the regulations were amendments to rules in place since 1999 and had been in the works for over a year.
"It was not (initiated by Beijing). Local law enforcement agencies started this," he told Reuters by telephone. But he added: "They definitely would have reported these upward. They'd definitely have sought opinions from the department in charge."
Tensions between China and the other claimants have flared since late November over these rules as well as China's new passports, which are imprinted with maps claiming sovereignty over the disputed territory.
Nevertheless, Chinese and foreign policy experts have said the two issues were not likely to be connected. And they are sceptical as to whether the new provincial regulations in Hainan represent a tougher stance from the central government, despite a once-a-decade change in the ruling Communist Party's top leadership last month.
"It's not consistent with some sort of new policy, or a policy shift. There's no evidence that way," said Zhu Feng, a professor at Peking University.
The Hainan regulations appear to allow border police to board and search vessels deemed to be operating illegally in what China considers Hainan's waters, but the full text of the regulations has not been made public and questions remain.
"The U.S. government very much wants clarification of what these rules mean, how they will be interpreted by the Hainan government and marine enforcement agencies and the purpose of these rules," Locke told Reuters on the sidelines of an investment forum in Beijing.
"It is really unclear, I think, to most nations," Locke said. "First we need clarification of the extent, the purpose and the reach of these regulations."
Hainan, which likes to style itself as China's answer to Hawaii or Bali with its resorts and beaches, is the province responsible for administering the country's extensive claims to the myriad islets and atolls in the South China Sea.
"This is pointed at neighbouring countries whose intrusions mainly around the Paracels are serious... In recent years more and more Vietnamese fishing boats have intruded into Paracel waters, and this is one aspect," Wu said.
"There was no (legal) basis for punishment before."
The rules would not influence the majority of ships passing through the South China Sea, he said.
"China's promises that foreign boats can enjoy freedom of navigation in the South China Sea aren't affected one bit by these new regulations, and they won't be affected by disputes in the South China Sea," he said. (Editing by Nick Macfie)