• The Philippines has deployed coast guard and aircraft against a Chinese research vessel.
• The Chinese Research Vessel Tan Suo 3 was detected entering Philippine waters.
• Legal actions were taken due to concerns over marine scientific research activities.

The Philippines has initiated a maritime enforcement operation in response to the presence of the Chinese Research Vessel (CRV) Tan Suo 3, which it claims has been conducting illegal marine scientific research within the country's exclusive economic zone (EEZ). Detected on May 1, 2025, the vessel was found approximately 92 nautical miles off the northern Ilocos coast, prompting the Philippine Coast Guard (PCG) to mobilize a coast guard vessel and an aircraft to escort the Chinese ship away from Philippine waters. "Their irregular movements were deemed inconsistent with the freedom of navigation," stated the PCG in its announcement, emphasizing violations of the country's sovereign rights, according to Channel News Asia, Reuters, and South China Morning Post.

During the operation, the PCG reported observing a deep-sea submersible named Shenhai Yongshi, also known as Deep-Sea Warrior, which was retrieved by the Chinese vessel. This submersible is capable of reaching depths of 4,500 meters and is typically used for deep-sea exploration. The PCG also noted the presence of a Rigid Hull Inflatable Boat recovering a yellow unidentified equipment piece potentially linked to marine research activities. The PCG asserted that these actions are indicative of illegal research operations conducted by China within the Philippine EEZ, lacking legal authorization, according to Channel News Asia, Reuters, and South China Morning Post.

The Chinese Embassy in Manila has yet to comment on these allegations. The PCG emphasizes that these unlawful activities constitute a significant challenge to the country's maritime sovereignty and exacerbate existing tensions in the already volatile South China Sea region, according to Channel News Asia, Reuters, and South China Morning Post.