Tensions in the South China Sea are rising, pitting China against smaller and weaker neighbors who all lay claim to islands, coral reefs and lagoons in waters rich in fish and potential gas and oil reserves. China's recent construction of artificial islands complete with airstrips and radar stations, and U.S. patrols challenging Beijing's vast territorial claims, have caused concern that the strategically important waters could become a flashpoint.
A look at some of the most recent key developments:
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.
PHILIPPINES, U.S. KEEP NERVOUS EYE ON SCARBOROUGH SHOAL
A tiny, uninhabited shoal the shape of a horseshoe just west of the northern Philippines ignited the latest round of provocative maneuvers in the South China Sea. The fate of Scarborough Shoal could now threaten to push the belligerents even closer to the tip of conflict.
Philippine Ambassador to Washington Jose Cuisia Jr. told reporters in Manila that a senior U.S. Navy official reported spotting a suspected Chinese survey ship at Scarborough Shoal a few weeks ago. Philippine officials fear it could be a prelude to turning the disputed coral reef into another man-made island that could cement China's hold of the land and pose a threat to the Philippines, just 145 miles (230 kilometers) to the east.
The shoal, 620 miles (1,000 kilometers) from the Chinese coast, is at the center of a case that Manila has filed with a U.N. tribunal in 2013, after Chinese coast guard ships took effective control of the land following a tense standoff with Philippine ships.
Cuisia said the Philippine military checked but found nothing, possibly because the Chinese ship later left the shoal.
He then asked Washington to help convince China not to build in Scarborough Shoal, saying the Philippines is not capable of stopping it alone.
U.S. Defense Secretary Ash Carter announced during a visit to Manila that for the first time U.S. ships had started conducting joint patrols in the South China Sea with the Philippines — a somewhat rare move not done with many other partners in the region.
The Pentagon also said that nearly 300 American troops, including Air Force commandos armed with combat aircraft and helicopters, will remain in the Philippines through the end of the month following annual war games that ended Friday.
China reacted angrily and accused the two countries of militarizing the region.
U.S. CARRIER BACK ON PATROL; CHINESE GENERAL VISITS ISLANDS
The United States and China are making some high-profile military moves in the South China Sea — each sending a message to the other that it won't back down.
U.S. Defense Secretary Ash Carter, after announcing stepped-up cooperation with the Philippines, flew to the John C. Stennis aircraft carrier as it headed back on patrol in the sea.
Carter stood alongside his Philippine counterpart, Voltaire Gazmin, as they watched U.S. Navy fighter jets launch into vivid blue skies about 70 nautical miles (130 kilometers) west of the island of Luzon.
At the same time, China's Defense Ministry said the country's second-ranking general, Fan Changlong, led military commanders to the Spratly Islands to visit troops and observe construction work.
The Pentagon also said it was aware of the reports that China has deployed Sheyang J-11 fighter jets to Woody Island in the Paracel Islands. Although such deployments are nothing new, Pentagon spokesman Cmdr. Bill Urban said they are "less the issue than the signal it sends of how far out of step China's actions are with the aspirations of the region."
CHINA DISPATCHES MILITARY PLANE TO DISPUTED MAN-MADE ISLAND
China's navy has dispatched a military plane to one of the country's man-made islands in the disputed South China Sea, the Defense Ministry said, in what is believed to be the first openly acknowledged mission of its kind.
A brief statement on the ministry's website said the plane was on patrol when it was diverted to Fiery Cross Reef on Sunday morning to pick up three injured construction workers.
The plane then flew to Sanya on China's southernmost island province of Hainan where it landed at Fenghuang International Airport, the ministry said.
Details about the plane and where it was based were not given, although a photo accompanying the report showed a four propeller Y-8 transport being met by an ambulance.
China completed the runway on Fiery Cross Reef last year and in January flew three commercial jets to the island as a test.
CHINA UNHAPPY WITH G7 MINISTERS' MENTION OF ISLAND-BUILDING
China has summoned diplomats from the Group of Seven industrialized nations to protest their statement condemning Beijing's island-building in the South China Sea.
The G-7 foreign ministers meeting in Japan expressed strong opposition to any "intimidating, coercive or provocative unilateral actions that could alter the status quo and increase tensions."
Chinese Ministry spokesman Lu Kang defended land reclamation work in the Spratly Islands as within its territorial rights, and accused the G-7 of diverging from its mission of safeguarding the global economy.
McCAIN: AMERICA NEEDS MORE THAN SYMBOLIC GESTURES IN SOUTH CHINA SEA
U.S. Sen. John McCain, a proponent of a robust response to contain China's territorial ambitions in the South China Sea, says it's time for the U.S. to show some teeth because, he says, Beijing has crossed all three red lines placed by the Obama administration. According to McCain, chairman of the Senate Armed Services Committee, China has pressed ahead with land reclamation, militarization and use of coercion.
Writing in London's Financial Times, the Arizona Republican says China will soon be confronted by a possible unfavorable ruling in a case brought by the Philippines at a U.N. tribunal, and "may use the coming months to secure its existing gains or pursue new forms of coercion to expand them."
This could include further reclamation and militarization at strategic locations including Scarborough Shoal, or declaration of an air defense identification zone over disputed territory, he said.
According to McCain, the U.S. must be prepared to challenge immediately any such moves, "move beyond symbolic gestures" and launch a robust freedom-of-navigation campaign that would increase the scope and pace of U.S. ships sailing close to China-controlled features.
"At present, the situation in the South China Sea is stable overall due to the common efforts of China and relevant regional countries. China resolutely opposes any country harming China's sovereignty and security and sabotaging peace and stability in the South China Sea under any conditions." — Chinese Foreign Ministry statement.
Associated Press writers Hrvoje Hranjski in Bangkok, Jim Gomez in Manila, Philippines, Christopher Bodeen in Beijing, and Lolita C. Baldor aboard the USS John C. Stennis contributed to this report.