Chinese personnel spotted on structure in disputed waters near Korean Peninsula

Sunlan No. 2, a structure installed by China in the Provisional Measures Zone in the West Sea, is seen in this photo released by Rep. Yi Byeong-jin of the Democratic Party of Korea, Wednesday. Courtesy of Rep. Yi Byeong-jin

Escalating a long-simmering maritime dispute, Chinese personnel have for the first time been identified on a contentious offshore structure built by Beijing in the West Sea’s Provisional Measures Zone (PMZ) — an overlapping area of the two nations’ exclusive economic zones.

The revelation, disclosed Wednesday by a Korean lawmaker, swiftly prompted calls in Seoul for the government to take countervailing measures against what was described as an increasingly assertive move by China.

Rep. Yi Byeong-jin of the ruling Democratic Party of Korea (DPK) disclosed recent photographs of the Chinese installation ahead of a parliamentary audit of the Coast Guard.

According to Yi, the photos show five individuals on the structure known as Sunlan No. 2, installed last year. Two people are visible on the upper deck, two are on the mid-left section, and one wearing a diving suit appears to be maintaining oxygen tanks near the waterline, he said.

Tensions in the Provisional Measures Zone have mounted as China intensifies its “gray zone” tactics in the area, including the construction of new structures near Ieodo — internationally known as Socotra Rock — a submerged reef located 149 kilometers southwest of Mara Island, Korea’s southernmost point, where the Korean and Chinese exclusive economic zones overlap. In an attempt to boost surveillance and counter Beijing’s expansion, the United States recently approached a Korean research group about providing a grant to install a powerful maritime radar in the contested waters.

Sunlan No. 2 has been a persistent source of friction between Korea and China after Seoul raised concerns that the structure could infringe on its maritime rights and alter the regional status quo.

While China insists the facility is purely for marine farming, Korea and its allies view it as part of a broader pattern of behavior. Yi questioned the nature of the activity, saying it did not resemble standard aquaculture operations.

"It is unusual for aquaculture farms to involve diving suits and oxygen equipment," Yi said. "A high-speed vessel carrying only a few people was also detected near the structure, raising further suspicion about its purpose."

Citing his experience as a legal scholar who graduated from Peking University, Yi argued that the West Sea structures could be part of China’s long-term bid to strengthen de facto control over disputed maritime areas, similar to the country’s expansion in the South China Sea. He further claimed that there could be potential military implications.

The lawmaker said he had previously sought budget allocations for a proportional response to China’s disputed structures in the West Sea, including 1 billion won ($699,000) for a research project and 60.5 billion won for the construction of Korea’s own structure. Although the proposals cleared a parliamentary committee, they were later struck during the final budget review.

Yi said the government risks letting the window of opportunity close on an effective response if it remains passive.

"There is a possibility that someone is residing in Sunlan No. 2," he said, "China will not withdraw unless we respond actively, and we must not miss the crucial window to defend our maritime sovereignty."