Chinese Maritime Safety Administration, or MSA, maritime law enforcement vessels in the waters east of Taiwan broadcast messages to three Taiwanese commercial vessels on June 7 and 9 inquiring about their origin and destination and asserting China's sovereignty over the waters, according to Taiwan's Coast Guard Administration, or CGA, on June 9. The CGA added that it instructed the three Taiwanese vessels to ignore the MSA requests, which they did, and the CGA responded to the MSA vessels by asserting Taiwan's sovereignty.

This comes after Japanese Prime Minister Sanae Takaichi and Philippine President Ferdinand Marcos Jr. announced on May 28 that they were starting talks to delimit their maritime borders east of Taiwan. China denounced this effort, and the MSA responded on June 6 by announcing a "special maritime traffic law-enforcement operation" in the waters east of Taiwan.