Security risks are rising in the South China Sea with an eruption of disputes over energy and sovereignty claims, experts say.
The problems of unsettled borders have dogged the region for years, but intensified exploration for offshore oil and gas has increased tensions with a series of incidents involving China in the past month.
"In the back of people's minds is the belief or hope that somehow, someday, somebody's going to strike it rich, so nobody's willing to give up the field," said Richard Bush, senior fellow in foreign policy studies at the Brookings Institution in Washington.
The latest conflicts began on May 26 when three Chinese patrol boats reportedly halted a seismic survey in waters claimed by Vietnam as part of its exclusive economic zone.
One of the boats cut a cable towed by a PetroVietnam survey ship, the state-owned oil company said. The confrontation took place 120 kilometers (80 miles) from Vietnam's coast and some 600 kilometers south of China's Hainan Island, according to the BBC.
Despite a Vietnamese protest, more incidents followed on May 31 as Chinese vessels tried to approach a second PetroVietnam ship and fired warning shots to scare off Vietnamese fishing boats on June 1, Thanh Nien Online said.
In a Foreign Ministry statement on May 28, China said it opposed Vietnam's oil and gas operations, "which have undermined China's interests and jurisdictional rights," the official Xinhua news agency reported. The ministry later dismissed the shooting reports as "sheer fabrication."
But the clashes have drawn angry demonstrations at China's diplomatic missions in Hanoi and Ho Chi Minh City, the former Saigon. Vietnam's deputy defense minister, Lt. Gen. Nguyen Chi Vinh, told reporters that the country would "use all means to protect our national sovereignty."
On June 9, Vietnam reported yet another incident off its southern coast, charging that a Chinese fishing boat tried to use a "cable cutting device" to stop another survey, Reuters reported. Vietnam's navy held live-fire exercises Monday in an area 40 kilometers off central Quang Nam province after warning other vessels to steer clear.
China's version of the June 9 event is that one of its fishing boats became tangled in survey gear and had to cut itself free. Foreign Ministry spokesman Hong Lei said Vietnam was operating illegally in areas under China's sovereignty.
But the episodes have been echoed by a statement from the Philippines on June 4, citing a series of protests over Chinese incursions since February.
The incidents involving fishing and oil exploration were "serious violations of Philippine sovereignty and maritime jurisdiction," Foreign Affairs Secretary Albert del Rosario said.
In one case, Manila said a Chinese ship opened fire to chase fishing boats from an area of the Spratly Islands claimed by the Philippines, the Associated Press reported.
Other incidents include reported flyovers by Chinese jets and the unloading of materials onto a reef in the disputed Spratlys, which China calls the Nansha Islands.
China's embassy in Manila denied the incursions but said a ship was "conducting normal maritime research activities." On June 8, China's spokesman said the Philippines "should stop publishing irresponsible statements that do not match the facts."
The Philippines Department of Foreign Affairs says it is particularly concerned about media reports that China plans to deploy a giant new deepwater oil rig in the South China Sea.
The ministry has asked China to specify the exact location, warning it should not be placed in Philippine waters, GMA News Online said.
In addition to China, Vietnam, and the Philippines, parts of the South China Sea are claimed by Malaysia, Brunei, and Taiwan.
Michael Swaine, senior associate at the Carnegie Center for International Peace, said the first task in dealing with the problems should be verification.
"It's very important to confirm clearly that, in fact, what is being reported ... is happening, and that it's being done at the behest of the Chinese government," Swaine said.
Chinese fishery authorities or oil companies may be acting on their own. It is also possible that Beijing has ordered a response to what it sees as assertive actions by its neighbors in disputed areas, he said.
A third possibility is that Beijing itself has become more assertive, as its neighbors claim. "I don't know, at this point, which of these three possibilities is true," said Swaine.
He noted that members of the Association of Southeast Asian Nations (ASEAN) had agreed to a nonbinding code of conduct in 2002, pledging to "exercise self-restraint in the conduct of activities that would complicate or escalate disputes."
At the annual Shangri-La Dialogue security conference in Singapore on June 5, China's defense minister, Gen. Liang Guanglie, promised to abide by the declaration, Reuters reported.
"If the Chinese indicate that they're not doing this ... then I think there's real cause for concern," Swaine said.
Speaking in Singapore, Liang cited improving relations with the United States as "cooperation partners," stressing that modernization of China's military will still leave it far behind other nations.
A 'freer hand'?
China has generally taken greater care to avoid disputes with the United States in the South China Sea since a March 2009 incident, when Chinese vessels tried to block the U.S. Navy surveillance ship Impeccable in international waters south of Hainan.
The latest episodes with Vietnam and the Philippines have raised some concern that Beijing may feel a freer hand in dealing with smaller countries as long it downplays differences with Washington.
"There may be a feeling in China that what the United States cares about is its own power, and China can take greater risks with its neighbors," said Bush of Brookings.
"The flaw in this line of thinking is that we have alliance relationships with some of its neighbors, we have partnership relations with others," he said. "So they're fooling themselves if they think we'll stay out of these little disputes because of their reassurance about their long-term intentions."
The frictions between Vietnam and China have also drawn the attention of Taiwan. On Saturday, Taiwan's Ministry of National Defense formed a task force to monitor the situation, the Central News Agency said.
At the Singapore conference, U.S. Defense Secretary Robert Gates made clear that Washington is keeping a close eye on the incidents.
"I fear that without rules of the road and without agreed approaches to dealing with these problems that there will be clashes," said Gates. "That serves nobody's interest."
Deepwater rig to be deployed
Nations in the region may be especially on edge because of last month's announcement that China has completed its first deepwater drilling platform after three years of work and an investment of 6 billion yuan ($923 million).
The 31,000-ton rig can operate in 3,000 meters (9,842 feet) of water with drilling depths of up to 12,000 meters, according to Xinhua. China National Offshore Oil Corp. (CNOOC) plans to start operations in the South China Sea next month.
Michael Herberg, energy security research director for the Seattle-based National Bureau of Asian Research, said that neighboring countries are watching anxiously to see where the rig goes.
"This is basically the same thing that every other oil company is doing, moving into the deep water," said Herberg. "But where they deploy that is obviously pretty critical."
"If they were to put that out in the South China Sea and act like they were going to drill in areas that are highly disputed by Vietnam, the Philippines, and others, then that's really going to escalate things," Herberg said.
Swaine believes it is more likely that China will keep the rig initially in northern uncontested waters. But Herberg says that "it's certainly possible that the government might try to use CNOOC, inching out into these areas to put a marker out" for asserting its claims.
For years, countries of the region have held out hopes that the offshore areas would yield vast volumes of oil and gas, but relatively little of these resources has been proven so far.
A significant deepwater discovery, even in uncontested waters, could increase the risk of conflict in disputed South China Sea sectors. The opposite outcome is also possible.
"If they hit dry holes, maybe the risk will decline," Bush said.