A look at recent developments in the South China Sea, where China is pitted against smaller neighbors in multiple disputes over islands, coral reefs and lagoons in waters crucial for global commerce and rich in fish and potential oil and gas reserves:

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EDITOR'S NOTE: This is a weekly look at the latest key developments in the South China Sea, home to several territorial conflicts that have raised tensions in the region.

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CHINA'S THINK TANK SAYS U.S. NAVAL OPERATIONS UNDERMINE ITS SOVEREIGNTY

China's government-backed institute for the South China Sea has released a report detailing an increase in U.S. military activities in the region, saying they threaten China's national security and undermine trust between Washington and Beijing.

According to the National Institute for South China Sea Studies , based on Hainan island province, the U.S. military has carried out more than 700 naval and aerial patrols in the region last year, deployed more advanced reconnaissance aircraft, drones, electronic surveillance ships and satellites as well as nuclear submarines and aircraft carriers.

"China has become the No. 1 targeted country of the U.S. close reconnaissance in terms of frequency, scope and means," the report said.

It said that the U.S. made more than 260 close reconnaissance sorties against China in 2009, and the number increased to more than 1,200 in 2014.

Such activities are "also very likely to lead to accidental collisions at sea or in the air, making it an important negative factor affecting Sino-U.S. relations and also peace and stability in the region," it said.

The report also notes U.S. military alliances and agreements with Japan, South Korea, the Philippines, Australia, Thailand and most recently, Vietnam.

The report said that from the U.S. perspective, China's large-scale construction activities in the South China Sea confirmed the U.S. suspicion that China intended to implement a strategy known as "anti-access/area denial," or actions designed to prevent an opposing force from entering an operational area or limit its freedom of actions within that area.

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PHILIPPINES WANTS TO BAN FISHING AT DISPUTED SHOAL

Philippine President Rodrigo Duterte, who has considerably reduced tensions with China over contested South China Sea waters, says he plans to declare a marine sanctuary at the disputed Scarborough Shoal. Such a move would keep away both Filipino and Chinese fishermen and prevent China from constructing any facilities, like it did on seven other features farther south in the Spratly archipelago.

Despite Duterte's wishes, China has not yet committed to such a proposal. Without Beijing's nod, it would be meaningless because since 2012, China has effective control of the tiny, uninhabited coral reef within the 200-mile Philippine exclusive economic zone.

Duterte relayed his marine sanctuary plan to Chinese President Xi Jinping during a meeting last week on the sidelines of an APEC summit in Peru, National Security Adviser Hermogenes Esperon Jr. said. Xi did not say whether he agreed.

Chinese Foreign Ministry spokesman Geng Shuang said that China had made "proper arrangement" for Filipinos to fish in nearby waters, and reiterated that "the sovereignty and jurisdiction over the Scarborough Shoal is not, and will not be, changed."

The Chinese coast guard continues to block the entrance to the horseshoe-shaped lagoon.

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AFTER VIETNAM, PHILIPPINES LOOKING TO UPGRADE ITS ISLAND FACILITIES

China has embarked on massive island-building in recent years in the South China Sea, drawing U.S. objections and protests from rival claimants, particularly the Philippines and Vietnam.

But according to satellite images, Vietnam also has extended a runway on Spratly Island and constructed new hangars, apparently to accommodate surveillance aircraft.

Now, the Philippines too is looking to construct a new port on Pag-asa Island, internationally known as Thitu, its biggest prize in the disputed Spratlys.

The Philippine Department of Transportation has earmarked $9 million for a seaport on the tiny island, which used to be a military installation in the 1970s and since then, home to about 200 civilians and 50 soldiers living in few dozen houses. It has a 1.3 kilometer (0.8-mile)-long runway but sea access is difficult because it is surrounded by shallow coral base.

In a report to the Philippine Congress, the Transportation Department said the new port would "vastly improve accessibility to the area and bolster the country's claims" in the South China Sea.

The Philippines had frozen all construction plans for the island until it won an international arbitration case against China in July that invalidated Beijing's claims to the South China Sea.

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CHINA TO OPEN 1ST SOUTH CHINA SEA MUSEUM

China has long cited ancient history as the basis for its claim to virtually the entire South China Sea. Now, it plans to open the first South China Sea Museum to exhibit antiques from early Chinese dynasties that were retrieved from the disputed waters.

Ten ceramic pieces, including dainty vases, incense holders, drinking vessels, dishes, cups and saucers from the Ming and Qing dynasties (1368-1911), were donated to the museum last week by two Chinese companies that purchased them at an auction in New York's Metropolitan Museum of Art in September, state-run Xinhua News Agency reported.

The museum, which is expected to open in March on south China's Hainan island province, also has received more than 800 pieces, including old compasses, logbooks and ceramics, that were found by fishermen, Xinhua said. Some date back to the 5th century and provide clues about trade along the maritime Silk Road, it said.

An international arbitration tribunal in July said that Beijing's claims are inconsistent with international law. It said that any historic rights were "extinguished" by the 1982 U.N. Convention on the Law of the Sea, which China ratified in 1996.

The tribunal said that while China had used islands in the past, it had never exercised exclusive authority over the waters. China has dismissed the ruling.

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Associated Press writer Jim Gomez in Manila, Philippines, contributed to this report.

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