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By Manuel Mogato and Ben Blanchard
MANILA/BEIJING, July 15 (Reuters) - A Chinese frigate grounded in disputed waters close to the Philippines was refloated on Sunday and headed back home, averting a possible standoff with the Philippines navy amid rising tensions in the strategically key South China Sea.
The South China Sea has become Asia's biggest potential military flashpoint as Beijing's sovereignty claim over the huge area has set it against Vietnam and the Philippines as the three countries race to tap possibly huge oil reserves.
In all, six parties have rival claims to the waters, which were a central issue at an acrimonious ASEAN regional summit last week that ended with its members failing to agree on a concluding statement for the first time in 45 years.
On Friday, the Chinese navy said one of its vessels had run aground on Half Moon Shoal, about 90 nautical miles (170 km) off the western Philippine island of Palawan, prompting Manila to send two of its vessels and reconnaissance aircraft to the area.
Beijing said its vessel had been on a routine patrol.
"At about 5 a.m. on July 15, the frigate which had run aground in waters near Half Moon Shoal successfully extricated itself with the help of a rescue team," China's defence ministry said in a statement.
"The bow has sustained light damage and everybody on board is safe. Its return to port is being organised. The incident caused no maritime pollution," the statement added, without providing further details.
The Philippines defence ministry confirmed the grounded vessel and about six other Chinese ships spotted in the area had left.
Manila says Half Moon Shoal falls well within its 200-nautical-mile exclusive economic zone, as recognised by international law.
"The incident in Hasa-Hasa shoal makes us nervous," Rommel Banlaoii, executive director of Philippine Institute for Peace, Violence and Terrorism Research, told Reuters, referring to Half Moon shoal in the Spratlys.
"I think what happened there was an accident, but we don't want such accident happening again because it could trigger something that all claimant states do not want to happen there."
"CREEPING" CHINA CONCERNS
Philippine defence and military officials say they are worried by China's "creeping" in disputed areas in the South China Sea, a violation of an informal code of conduct adopted in Cambodia in 2002.
The two countries have faced-off on a number of occasions in the disputed waters, and earlier in the year they were involved in a month-long standoff at Scarborough Shoal, about 500 km north of Half Moon Shoal.
Last year, the Philippines scrambled aircraft and ships to the Reed Bank area after Chinese navy ships threatened to ram a Philippine survey ship.
Beijing said last month it had begun "combat-ready" patrols in waters it said were under its control in the South China Sea, after saying it "vehemently opposed" a Vietnamese law asserting sovereignty over the Paracel and Spratly islands.
The stakes have risen in the area as the U.S. military shifts its attention and resources back to Asia, emboldening its long-time ally the Philippines and former foe Vietnam to take a bolder stance against Beijing.
The United States has stressed it is neutral in the long-running maritime dispute, despite offering to help boost the Philippines' decrepit military forces. It says freedom of navigation is its main concern about a waterway that carries $5 trillion in trade -- half the world's shipping tonnage.
At last week's Association of Southeast Asian Nations (ASEAN) meeting, Cambodia sided with China and prevented the 10-nation bloc from issuing a customary concluding statement that covers achievements and concerns -- this year, that primarily involved the South China Sea. (Writing by Jeremy Laurence)