Q&A: South China Sea dispute
Rival countries have wrangled over territory in the South China Sea for centuries - but a recent upsurge in tension has sparked concern that the area is becoming a flashpoint with global consequences.
What is the argument about?
It is a dispute over territory and sovereignty over ocean areas and the Paracels and the Spratlys - two island chains claimed in whole or in part by a number of countries. Alongside the fully fledged islands, there are dozens of uninhabited rocky outcrops, atolls, sandbanks and reefs, such as the Scarborough Shoal.
Who claims what?
China claims by far the largest portion of territory - an area defined by the "nine-dash line" which stretches hundreds of miles south and east from its most southerly province of Hainan. Beijing has said its right to the area come from 2,000 years of history where the Paracel and Spratly island chains were regarded as integral parts of the Chinese nation.
In 1947 China issued a map detailing its claims. It showed the two island groups falling entirely within its territory. Those claims are mirrored by Taiwan, because the island considers itself the Republic of China and has the same territorial claims.
Vietnam hotly disputes China's historical account, saying China had never claimed sovereignty over the islands before the 1940s. Vietnam says both island chains are entirely within its territory. It says it has actively ruled over both the Paracels and the Spratlys since the 17th Century - and has the documents to prove it.
The other major claimant in the area is the Philippines, which invokes its geographical proximity to the Spratly Islands as the main basis of its claim for part of the grouping.
Both the Philippines and China lay claim to the Scarborough Shoal (known as Huangyan Island in China) - a little more than 100 miles (160km) from the Philippines and 500 miles from China.
Malaysia and Brunei also lay claim to territory in the South China Sea that they say falls within their economic exclusion zones, as defined by UNCLOS. Brunei does not claim any of the disputed islands, but Malaysia claims a small number of islands in the Spratlys.
Why are so many countries so keen?
The Paracels and the Spratlys may have vast reserves of natural resources around them. There has been little detailed exploration of the area, so estimates are largely extrapolated from the mineral wealth of neighbouring areas.
Chinese officials have given the most optimistic estimates of resource wealth in the area. According to figures quoted by the US Energy Information Administration, one Chinese estimate puts possible oil reserves as high as 213 billion barrels - 10 times the proven reserves of the US. But American scientists have estimated the amount of oil at 28 billion barrels.
According to the EIA, the real wealth of the area may well be natural gas reserves. Estimates say the area holds about 900 trillion cubic ft (25 trillion cubic m) - the same as the proven reserves of Qatar.
The area is also one of the region's main shipping lanes, and is home to a fishing ground that supplies the livelihoods of thousands of people.
How much trouble does the dispute cause?
The most serious trouble in recent decades has flared between Vietnam and China. The Chinese seized the Paracels from Vietnam in 1974, killing more than 70 Vietnamese troops. In 1988 the two sides clashed in the Spratlys, when Vietnam again came off worse, losing about 60 sailors.
The Philippines has also been involved in a number of minor skirmishes with Chinese, Vietnamese and Malaysian forces.
The most recent upsurge in tension has coincided with more muscular posturing from China. Beijing officials have issued a number of strongly-worded statements, including warning their rivals to stop any mineral exploration in the area.
The Philippines has accused China of building up its military presence in the Spratlys. In early 2012, the two countries engaged in a maritime stand-off, accusing each other of intrusions in the Scarborough Shoal. Chinese and Philippine vessels refused to leave the area for a number of weeks, leading to rhetoric and protests.
In July 2012 China formally created Sansha city, an administrative body with its headquarters in the Paracels which it says oversees Chinese territory in the South China Sea - including the Paracels and the Spratlys. Both Vietnam and the Philippines protested against this move.
In November 2012, China granted its border patrol police in Hainan the power to board and search foreign ships stopping in its waters or violating other regulations.
Unverified claims that the Chinese navy deliberately sabotaged two Vietnamese exploration operations in late 2012 led to large anti-China protests on the streets of Hanoi and Ho Chi Minh City. Vietnam said it would be sending patrols to accompany its fisheries in the area. It also has held live-fire exercises off its coast - an action that was seen as a gross provocation by Beijing.
Vietnam was also one of a number of nations that refused to stamp new editions of Chinese passports which include a map showing disputed areas of the South China Sea as Chinese territory.
In January 2013, Manila said it was taking China to a UN tribunal under the auspices of the UN Convention on the Laws of the Sea, to challenge its claims in the South China Sea.
Manila said it had exhausted "almost all political and diplomatic avenues" with Beijing in the dispute. China insists the dispute should be resolved through direct negotiation.
Is anyone trying to resolve the row?
Over the years, China has tended to favour arrangements negotiated behind closed doors with the individual leaders of other countries. But the other countries have pushed for international mediation.
So in July 2010, when US Secretary of State Hillary Clinton became involved in the debate and called for a binding code of conduct, China was not pleased. The Chinese Foreign Ministry dismissed her suggestion as an attack on China.
Agreements such as the UN's 1982 convention appeared to lay the framework for a solution. But in practice, the convention led to more overlapping claims, and did nothing to deter China and Vietnam in pressing their historical claims.
Even if the Philippines is successful in its attempts to pursue China at a UN tribunal, the terms of the convention mean China would not be obliged to abide by the ruling.
Both the Philippines and Vietnam have made bilateral agreements with China, putting in place codes of conduct in the area. But the agreements have made little difference.
The regional grouping Asean - whose membership includes all of the main players in the dispute except China and Taiwan - concluded a code of conduct deal with China in 2002.
Under the agreement, the countries agreed to "resolve their territorial and jurisdictional disputes by peaceful means, without resorting to the threat or use of force, through friendly consultations and negotiations".
But recent events suggest that Vietnam and China at least have failed to stick to the spirit of that agreement. And recent attempts by Asean to discuss new ideas for resolving the dispute appear to have left the bloc severely divided.