The South China Sea is one of the world’s most economically important waterways, and increasingly one of Asia’s biggest flashpoints.

The sea, which stretches across 3.5m sq km (1.35m sq miles), is a busy shipping lane, with trillions of dollars’ worth of trade passing through it every year. It is also rich in fish, and thought to contain significant reserves of oil and gas.

But the sea, and the various reefs, islands and rocks that sit within it, are subject to a long-running and fierce territorial dispute. China claims a large portion of the sea as its own, ignoring a Hague tribunal finding from 2016 that its sweeping claims are without legal grounding. Since 2013 it has undertaken huge construction work, building militarised artificial islands in the area. Other countries also have overlapping claims, including the Philippines, a US treaty ally, which has repeatedly accused Chinese vessels of dangerous, aggressive behaviour at sea, and Vietnam, which is now conducting rapid island-building work. Malaysia, Brunei and Taiwan also have competing claims.

Below is a list of the key land formations in the area, who controls them, the confrontations and why they matter.

Second Thomas Shoal

• Location: 194km (105 nautical miles) from the Philippine island of Palawan, within the Philippines’ exclusive economic zone (EEZ)*.

• Occupied by: the Philippines, but it has been subject to what analysts say is in effect a blockade by China.

• Claimed by: the Philippines, China, Taiwan and Vietnam.

• What’s there: A rusting second world war-era ship, the BRP Sierra Madre, which was deliberately grounded by the Philippines in 1999 and now serves as an unlikely military outpost.

• Why it matters: for the Philippines, the Sierra Madre serves as a symbol of the country’s defiance against Chinese expansionism. However, it is in a dilapidated state and some analysts warn it could be on the verge of collapse. China has repeatedly blocked Philippine resupply missions to the shoal, in an attempt to stop the delivery of construction materials needed to reinforce its structure.

• Recent confrontations: Since February 2023, the Philippines has accused China of aggressive and unsafe behaviour on eight occasions in the area around Second Thomas Shoal, including firing a military-grade laser and water cannon at Philippine Coast Guard crew and ramming its boats. Most recently, in June 2024, the Philippines accused China Coast Guard vessels of ramming, towing and puncturing its boats with knives, looting disassembled firearms, destroying communication and navigational equipment and confiscating cellphones of personnel. One Navy officer lost a thumb in the incident.

Scarborough Shoal

• Location: 230km (124 nautical miles) from the Philippine island of Luzon, within the Philippines’ EEZ.

• Occupied by: China’s coast guard has maintained a continual presence there since 2012, when it seized the feature following a two-month standoff with Philippine ships.

• Claimed by: Philippines, China and Taiwan.

• What’s there: China has not built any structures on the shoal, as it has at other features it controls in the South China Sea.

• Why it matters: The seizure of Scarborough Shoal, a rich fishing ground, in 2012 was one of the factors that prompted the Philippine government to refer the dispute to international arbitration. A tribunal in the Hague in 2016 ruled in the Philippines’ favour, finding that China’s expansive claims in the South China Sea were invalid.

• Recent confrontations: In February, the Philippines Coast Guard accused its Chinese counterpart of carrying out dangerous manoeuvres to block its vessels near Scarborough Shoal. China has been accused of putting up floating barriers to cut off Filipino boats from accessing the waters, and of swarming in the area and harassing Filipino fishing boats.

Thitu Island

• Description: an island that is less than a mile long.

• Location: 426km (230 nautical miles) west of the Philippine province of Palawan.

• Occupied by: the Philippines.

• Claimed by: the Philippines, Vietnam, Taiwan and China.

• What’s there: Thitu is home to about 250 people, and has internet and mobile connectivity, a runway, port, school, gymnasium and evacuation centre in case of typhoons.

• Why it matters: the largest of the Philippine-administered features in the Spratlys, and the Philippines government has encouraged fishing communities to move there. The China Coast Guard and maritime militia regularly patrol in the surrounding waters.

Sabina Shoal

• Description: a coral atoll 22km (12 nautical miles) long.

• Location: 139km (75 nautical miles) from the coast of Philippine island Palawan, within the Philippines’ EEZ.

• Occupied by: unoccupied

• Claimed by: the Philippines, China and Taiwan

• What’s there: The Philippine Coast Guard’s most modern vessel, the 97-metre Teresa Magbanua, has been stationed there since April to monitor alleged reclamation activities by China. In response China, which denies reclamation activities, has deployed its 12,000-tone, 165-metre Coast Guard Ship, nicknamed “the Monster” due to its size. It has been there since 3 July and is less than 800 metres away from Teresa Magbanua.

• Why it matters: Sabina Shoal is close to Reed Bank, which is believed to be rich in oil and gas. It also serves as the rendezvous point for vessels carrying out resupply missions to Filipino troops at Second Thomas Shoal.

China’s ‘big three’ in the Spratly Islands: Mischief Reef, Subi Reef and Fiery Cross

• Description: Militarised reefs converted into artificial islands, reclaiming 558 hectares (1,379 acres), 395 hectares (976 acres) and 274 hectares (677 acres) respectively.

• Location: in the Spratly islands. A UN tribunal in 2016 ruled that Mischief Reef was underwater prior to China’s reclamation and therefore part of the Philippines’ EEZ.

• Claimed by: China, Taiwan, Philippines and Vietnam

• Occupied by: China

• What’s there: These reefs feature anti-ship and anti-aircraft missile systems, laser and jamming equipment and fighter jets, according to the US. Underground storage tunnels have also been built.

Reed Bank

• Description: Reed Bank is an isolated underwater volcanic mountain

• Location: Reed Bank is about 157km (85 nautical miles) from the coast of Palawan, within the Philippines’ EEZ.

• Claimed by: the Philippines, China and Taiwan.

• What’s there: Located in an area thought to be rich in oil and gas. The Philippines has accused China of causing severe damage to the marine environment and coral at Iroquois Reef, located at the southern end of Reed Bank, and has said it is considering legal options.

• Why it matters: The site is crucial to the Philippines which faces a looming energy crisis as its Malampaya gas field, which supplies a fifth of the power for the country’s main island of Luzon, is almost depleted. Exploration has been on hold for years due to the tensions with China.

• Recent confrontations: China’s maritime militia has been described as conducting “theft by soft occupation” at Iroquois Reef, where boats have rafted together intermittently to form a floating outpost. The China Coast Guard has also conducted patrols.

Paracel islands

• Description: an archipelago of over 130 coral islands, shoals and reefs

• Location: in the north of the South China Sea, about 370 km (200 nautical miles) to the south-east of China’s Hainan province.

• Claimed by: China, Vietnam and Taiwan

• Occupied by: China

• What’s there: China has 20 outposts in the Paracel Islands which are crucial to its surveillance activities in the South China Sea. These have been developed with protected harbours that can host large numbers of naval and civilian vessels, and helipads. The largest of the Paracels, Woody Island, is home to at least 1,000 Chinese nationals and sports an airstrip, hangars and a deployment of HQ-9 surface-to-air missile batteries, according to the Asia Maritime Transparency Initiative (AMTI).

Whitsun Reef

• Description: a v-shaped reef in the Spratly Islands.

• Location: around 324km (175 nautical miles) off the coast of the Philippine island of Palawan, within the country’s EEZ.

• Claimed by: China, Philippines and Vietnam

• Occupied by: Unoccupied

• What’s there: Maritime militia ships raft together and form a floating outpost in the area, maintaining a continuous presence that is reduced only during the Lunar New Year, according to SeaLight, which monitors the waters.

Vanguard Bank

• Description: a submerged feature that hosts three Vietnamese outposts.

• Location: within Vietnam’s EEZ

• Claimed by: Vietnam, China, and Taiwan

• Occupied by: Vietnam

• What’s there: Vietnamese offshore oil and gas fields. China is accused of carrying out persistent and intrusive patrols in the area.

Luconia Shoals

• Description a group of coral reef platforms and small atolls.

• Location: southernmost part of the Spratly Islands and within Malaysia’s EEZ.

• Claimed by: China, Malaysia and Taiwan.

• Occupied by: controlled by Malaysia.

• What’s there: Malaysia’s offshore oil and gas fields. China is accused of carrying out persistent and intrusive patrols in the area.

Barque Canada Reef

• Description: a narrow coral atoll in the southern part of the Spratlys. It has almost doubled in size over the past six months, from 96 hectares (238 acres) to 167 hectares (412 acres), as Vietnam accelerates its expansion of outposts, according to AMTI.

• Location: located more than 370km (200 nautical miles) west of the islands of Borneo and Palawan.

• Occupied by: Vietnam.

• Claimed by: Barque Canada Reef is claimed by China, Malaysia, the Philippines, and Vietnam.

• Why it matters: Barque Canada Reef is the only Vietnamese outpost so far with the potential to host a 3,000-metre runway suitable for larger military aircraft. Vietnam is rapidly expanding its features in the South China Sea; so far this year it has created almost as much new land as it did in the previous two years combined, according to AMTI’s research.

*Exclusive economic zone – the waters that stretch for 200 nautical miles (370km) from a nation’s coastline, and where a country has special rights to exploit resources and build.