Tensions in the South China Sea are rising, pitting China against smaller and weaker neighbors that 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 in the Spratly archipelago, 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 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.
CHINA DEFENDS MILITARY PLANE LANDING
China says the United States is overblowing a humanitarian emergency mission that involved one of its military planes landing on an artificial island — which also happens to be one of three recently built military outposts with long runways.
The Y-8 transport aircraft made a trip to Fiery Cross Reef in the Spratlys to evacuate three injured construction workers, according to the Ministry of Defense.
State Department spokesman John Kirby questioned the need for a military aircraft, citing concern that China keeps militarizing the disputed region. He said the injured workers were involved in infrastructure improvements of a military nature.
"One could argue that it's just another sign that the Chinese are willing to keep militarizing the effort in general," he told reporters.
China's Defense Ministry said it was completely within the mission of the People's Liberation Army to rescue people — and carry out construction activities and deployment of defense facilities on related islets and reefs in the Nansha Islands, the Chinese name for the Spratlys.
FISHERMEN REPORT MORE CHINESE SHIPS; U.S. FLIES FIRST MISSION FROM PHILIPPINES
Filipino fishermen say they've seen more Chinese coast guard ships than usual around the contested Scarborough Shoal, which China effectively took over in 2013 after a tense standoff with Philippine vessels.
Although fishermen have been complaining they're being driven away by Chinese ships, the Philippine Department of Defense said it could not confirm an increase in Chinese presence at the shoal, 145 miles (230 kilometers) from Luzon island.
Meantime, the U.S. Air Force flew its first mission over the Scarborough area as part of a new Air Contingent force stationed in the Philippines. It involved four A-10C Thunderbolt jets and two Sikorsky HH-60 helicopters.
The mission: establishing air and maritime "domain awareness" and "assuring all nations have access to air and sea domains throughout the region in accordance with international law," according to a U.S. military statement.
Free navigation "is extremely important, international economics depends on it — free trade depends on our ability to move goods," said Col. Larry Card, commander of the Air Contingent, part of stepped-up U.S. assistance to its Philippine ally.
RUSSIA, SOME ASEAN NATIONS BACK CHINA; BRITAIN STANDS BY U.S.
As China and other claimants await the ruling of a U.N. tribunal on a case filed by the Philippines that challenges Beijing's vast territorial claims, world and regional players are lining up behind one side or the other.
China has refused to take part in the proceedings at the U.N. Court of Arbitration, and it's not clear how the ruling can be enforced.
Russian Foreign Minister Sergey Lavrov, meeting with his Chinese counterpart in Moscow, said Russia is against any interference from third parties — a reference to the U.S. — " or any attempts to internationalize these disputes."
Russia repeated China's position that "only parties can resolve their dispute through direct talks."
Britain, on the other hand, says it will stand alongside the U.S. in supporting the ruling.
Hugo Swire, British minister of state for the Foreign Office, told a Washington think tank that growing tensions in the South China Sea are driven by China's assertive actions. He said any ruling by the court should be binding on both parties.
In Southeast Asia, which is broadly divided between pro- and anti-China blocs, Chinese Foreign Minister Wang Yi said Beijing had reached a consensus with Brunei, Cambodia and Laos — its traditional allies — on the South China Sea issue.
The four countries say territorial disputes are not an issue between China and the 10-member Association of Southeast Asian Nations and should be resolved by parties directly.
Chinese Foreign Ministry spokeswoman Hua Chunying said earlier that the case filed by the Philippines is an attempt to deny China's sovereignty over the Spratly Islands and "an abuse of international law."
U.S. ADMIRAL DENIES RIFT WITH THE WHITE HOUSE
The Pacific Fleet commander Adm. Harry Harris has denied reports of differences with the White House in strategy over the South China Sea.
Navy Times reported on a gag order issued to military commanders for comments about the South China Sea in the run-up to the nuclear summit in Washington that included China.
Harris said in a statement that "any suggestion that the White House has sought to 'tamp down' on my talking about my concerns is patently wrong."
He said that during recent congressional testimony and press engagements in Washington, "I was very public and candid about my concerns regarding many issues in the Indo-Asia-Pacific to include the fact that China's militarization of the South China Sea is problematic."
"The United States and Vietnam share the interest in maintaining peace and stability in the region. So does China. But its massive land reclamation project in the South China Sea and increasing militarization of these outposts fuel regional tension and raise serious questions about China's intentions." — U.S. Deputy Secretary of State Antony Blinken, speaking on a visit to Hanoi.
Associated Press writers Hrvoje Hranjski in Bangkok, Christopher Bodeen in Beijing, Tran Van Minh in Hanoi, Vietnam, and Jim Gomez in Manila, Philippines, contributed to this report.
Follow Hranjski on Twitter at twitter.com/hatbangkok