On Tuesday (December 30), the Philippine Coast Guard (PCG) announced that a Chinese deep-sea research vessel was found off the coast of Cagayan province in the northern part of Luzon Island. The PCG has dispatched light aircraft for aerial surveillance and requested the Chinese vessel, named “Explorer II,” to explain whether it was conducting marine research activities in the Philippines’ exclusive economic zone without consent. However, there has been no response from the Chinese vessel.
The PCG spokesperson, Jay Tarriela, mentioned that the Philippines utilized Canada’s Dark Vessel Detection System to detect the Chinese research vessel within the Philippine Exclusive Economic Zone (EEZ).
In response, PCG Commander Ronnie Gil Gavan ordered an “Islander” light aircraft to immediately conduct Maritime Domain Awareness (MDA) flight missions to identify the vessel and determine its intentions.
During the patrol, the pilot made multiple radio calls to the vessel, questioning its navigational purpose and reminding that conducting marine scientific research in Philippine waters requires prior approval. Engaging in research activities without permission would violate Philippine maritime laws and the United Nations Convention on the Law of the Sea (UNCLOS).
However, the Chinese vessel did not respond to any radio calls.
The PCG further explained that during the patrol, the aircraft visually confirmed that the “Explorer II” was heading east approximately 55.8 nautical miles off the coast of Santa Ana in Cagayan province. The vessel, with a length of 87.25 meters, serves as a deep-sea research platform supporting manned and unmanned submersibles for deep-sea exploration missions. Earlier this month, the vessel departed from Hainan Province, China, entered the western waters of the Philippine EEZ, and continued eastward.
This incident occurred amidst escalating security tensions in the Indo-Pacific region.
Cagayan province, located at the northern tip of Luzon Island near Taiwan, houses a military base available for use by the US military under the Enhanced Defense Cooperation Agreement (EDCA).
On Tuesday, the Chinese military conducted military exercises near Taiwan under the codename “Just Mission-2025,” launching rockets into the surrounding waters and simulating strike and blockade operations. The timing of the exercise came shortly after the United States announced a record-breaking $11 billion arms sale to Taiwan.
The Chinese Embassy in Manila responded, stating that the vessel was engaged in routine navigational exercises and expressing China’s rejection of certain domestic maritime laws of the Philippines, claiming rights under international law to pass through relevant waters.
The Philippine Coast Guard noted that in recent weeks, Chinese research vessels have frequently appeared in Philippine waters, especially in the Western Philippine Sea. In 2025 alone, over twenty Chinese research vessels have been monitored entering the Philippine EEZ.
The PCG emphasized that following the instructions of Philippine President Ferdinand Marcos Jr., they would uphold national sovereignty and maritime laws, continuously monitor unauthorized maritime activities and take necessary actions.