The Philippine Coast Guard (PCG) raised concerns over the presence of the Chinese research vessel Tan Suo 3 near Ilocos Norte, citing its deep-sea mapping capabilities which could aid in submarine operations. According to Commodore Jay Tarriela, the ship was detected conducting unauthorized marine scientific research within the Philippine exclusive economic zone (EEZ).
Tarriela emphasized that while the mapping is presented as scientific activity, its potential to assist submarine navigation poses a serious security threat.
On May 1, the Tan Suo 3 was first spotted 92 nautical miles off the coast of Burgos, Ilocos Norte. The PCG deployed BRP Teresa Magbanua and an aircraft to monitor and escort the vessel out of Philippine waters. During the operation, they also observed the Deep-Sea Warrior (Shenhai Yongshi) submersible being deployed and recovered by the Chinese ship — a device capable of diving up to 4,500 meters deep.
Additionally, the PCG noted the retrieval of an unidentified yellow device, which may be part of the ship’s scientific activities.
As of 10 a.m. Tuesday, the vessel was 250 nautical miles off Burgos, now beyond the Philippine EEZ. The incident underscores ongoing tensions in the West Philippine Sea, where China continues to assert broad territorial claims despite a 2016 arbitral ruling favoring the Philippines.