Vietnam has condemned China’s land reclamation activities at the Antelope Reef in the disputed Paracel Islands, following reports of accelerated dredging, landfilling and construction operations that a US-based think tank said could make it “the largest Chinese feature” in the South China Sea.
“Any foreign activity carried out in Hoang Sa, including Hai Sam Reef, without Vietnam’s permission is completely illegal and invalid,” Vietnamese Foreign Ministry spokeswoman Pham Thu Hang said Saturday, referring to the archipelago and reef claimed by Hanoi and Beijing, as well as Taiwan, by their Vietnamese names. “Vietnam resolutely opposes such activities.”
Last week, the Asia Maritime Transparency Initiative, or AMTI, a project of the Center for Strategic and International Studies, or CSIS, in Washington, released an analysis of satellite images that found extensive land reclamation efforts underway at Antelope Reef over the past month could make the reef suitable for construction of a 9,000-foot (2,700-meter) airstrip.
Beijing has built several airstrips of this size on other islands in the South China Sea, including in the Spratly Islands, another disputed archipelago, according to the AMTI report.
Territorial hot spot
Although sovereignty over the Paracels is disputed, China took effective control of the archipelago after a 1974 naval clash with South Vietnam, which lost the Vietnam War to North Vietnam the following year.
Called the Xisha Islands by Beijing, the island chain is now one of several hotspots in the South China Sea, where several countries have overlapping territorial and maritime claims.
In early 2026, media highlighted new Chinese dredging and dumping activities at Antelope Reef. Previously, it was one of the smallest Chinese outposts in the region.
Beijing began major dredging work in October 2025 and has launched what appears to be preliminary construction of an airstrip in recent weeks, including more than 50 small gray-roofed structures and a helipad near the lagoon entrance, as well as the foundations of larger buildings and several piers, according to the report.
AMTI estimates that the reclaimed land at Antelope Reef measures approximately 1,490 acres (6.02 square kilometers), close to the 1,504 acres (6.09 square kilometers) of Mischief Reef, China’s largest outpost in the South China Sea. For comparison, Woody Island – the largest Chinese-held island in the Paracels – measures approximately 890 acres (3.60 square kilometers).
“If construction progresses at the pace seen in satellite images, Antelope Reef is on track to become China’s largest reef in the Paracels and potentially in the entire South China Sea, matching or even surpassing the size of Mischief Reef in the Spratlys,” the report said.
Antelope Reef Lagoon could also accommodate a larger maritime presence.
“This could allow more coast guards and large numbers of maritime militia to maintain a presence on the reef, as has been common in recent years at Mischief Reef,” AMTI said.
The Antelope Reef is located approximately 162 nautical miles (300 kilometers) from the port of Sanya, in China’s Hainan province, and 216 nautical miles (400 kilometers) from Da Nang, Vietnam. Sanya is a major base for Chinese naval and air forces that monitor the South China Sea, underscoring the location’s strategic importance.
The law of the sea
China’s expansion of the reef does not necessarily strengthen its claims to the Paracels from a legal perspective, according to Josue Raphael J. Cortez, faculty and internship coordinator at the School of Diplomacy and Governance at De La Salle-College of Saint Benilde in the Philippines.
“Indeed, if we want to use UNCLOS as the basis of a country’s maritime rights, the basis is and always will be the natural conditions of these elements,” he told Radio Free Asia, referring to the United Nations Convention on the Law of the Sea.
Adopted in 1982 and in force since 1994, UNCLOS is the main international legal framework governing maritime rights. Because it relies heavily on “naturally formed” land features to define each country’s exclusive economic zone and territorial seas, artificial expansion does not automatically create new legal rights.
Cortez also said regional reactions would be closely monitored, particularly given the reef’s proximity to Vietnam.
“Given that the reef is close to the Vietnamese part of the South China Sea, it will be an interesting opportunity for the region to get a sense of how such a move will be perceived,” he said.
The development also comes amid renewed tensions elsewhere in the South China Sea, particularly between China and the Philippines over competing sovereignty claims.
Manila recently rejected Beijing’s claims to disputed territory including Scarborough Shoal, insisting that the Philippines’ claims are based on international law. China, for its part, has objected to what it calls “misrepresentations” of its position.
The shoal is a triangular chain of reefs and lagoons off the west coast of the Philippines, which China has maintained control of since a 2012 standoff.
Manila continues to assert its rights under international law, including a 2016 arbitral ruling that found Beijing’s claims to much of the South China Sea had no legal basis.
Edited by Eugene Whong.