By Li Xian | 2025-05-01

South Korean officials are expressing increasing concern about three substantial steel structures China has erected in a contested area of the Yellow Sea (known in South Korea as the West Sea).

Seoul contends the structures are a strategic move by Beijing to assert control over disputed waters.

These controversial structures are located within a Provisional Measures Zone (PMZ), an area where the exclusive economic zones (EEZs) of South Korea and China overlap.

China has installed three structures in the shared PMZ without informing Seoul, despite a 2001 agreement that restricts the area to fishing and navigation.

These structures include two deep-sea salmon farms and a converted oil rig, which Beijing calls a "support facility." Each of these features a polygonal framework at least 70 meters in diameter and extends several stories high.

Vessel standoff

Adding to Seoul's apprehension, a South Korean fishery patrol vessel discovered a new offshore structure in March 2022 that bears a striking resemblance to an oil drilling platform.

According to a report by Chosun Ilbo, this particular platform has undergone noticeable expansion since 2024.

It now measures roughly 100 meters wide and 80 meters long, and features a helipad and three steel bridges, with the capacity to accommodate more than 100 individuals. The report stated that the Chinese converted the facility from a decommissioned oil rig.

The Chinese coast guard and civilian vessels consistently have thwarted South Korean attempts to inspect these sites.

One such incident occurred in late February when a South Korean research vessel approaching the area confronted a Chinese coast guard ship and three rubber boats, resulting in a tense two-hour standoff.

South Korean officials fear the semipermanent platform is part of a larger "salami-slicing" strategy to gradually shift the status quo in the Yellow Sea to China's advantage, a tactic they have observed in China's ongoing dispute with the Philippines in the South China Sea, according to Newsweek.

Reciprocal measures

In response to these developments, South Korea's Foreign Ministry conveyed its "deep concern" during a bilateral maritime dialogue on April 23.

The ministry emphasized that South Korea's "legitimate maritime rights should not be infringed" and demanded the removal of all three Chinese structures, stating that any new constructions in the disputed waters would be unacceptable.

Chinese Foreign Ministry spokesperson Guo Jiakun responded by insisting the structures are for aquaculture purposes and do not violate the fishery agreement. They are unrelated to maritime boundary issues, he said.

However, observers are voicing significant skepticism.

The platform's true purpose might be oil exploration, Shu Hsiao-huang, an associate research fellow at Taiwan's Institute for National Defense and Security Research, told Focus.

Based on its size, "it is impossible the structure is related to fish farming," he said, drawing a parallel to China's strategy of deploying oil platforms to assert control in the South China Sea.

Under the United Nations Convention on the Law of the Sea (UNCLOS), coastal states have jurisdiction over facilities built within their own EEZ, Lin Ting-hui, deputy secretary-general of the Taiwan Society of International Law, explained, echoing those concerns.

"China's objective is clearly to seize substantial sovereign rights over the EEZ, including ownership of resources and jurisdiction," he told Focus.

"This is a clandestine tactic to claim our waters inch by inch and restrict the operations of the US-South Korea alliance," said Jaewoo Choo, director of the China Research Center at the Korea Research Institute for National Security, in an April 21 Financial Times report.

In response to the escalating tensions, South Korean Foreign Minister Cho Tae-yul announced on April 28 that Seoul was considering reciprocal measures, such as constructing its own aquaculture installations or a marine science research base in the disputed area.

The South Korean National Assembly has further approved an additional budget of 60.5 billion KRW ($44 million) to counter China's moves.