The Philippine Coast Guard (PCG) warned a Chinese vessel allegedly conducting illegal marine research in Philippine territory.

Footage shows PCG personnel issuing a radio challenge to the Chinese research vessel (CRV) Tan Suo 3 seen lurking 92 nautical miles off Ilocos Norte, on May 1.

An aircraft was also deployed to shadow the Chinese vessel's movements.

In a statement, PCG spokesman Commodore Jay Tarriela said: 'Their irregular movements were deemed inconsistent with the freedom of navigation and indicative of marine scientific research activities, which violate the sovereign rights of the Philippines.They were instructed to cease their unlawful activities, clarify their intentions, and ensure continuous transit within the EEZ in compliance with both international and Philippine laws.'

The Tan Suo 3 was reportedly spotted collecting a deep-sea submersible, the SHENHAI YONGSHI, capable of diving up to 2.8 miles underwater for scientific research. It also dispatched a rigid hull inflatable boat to recover what is believed to be marine research equipment.

The PCG said: 'These actions of the CRV serves as clear evidence that the People's Republic of China are conducting illegal marine scientific research activities within the Philippines' Exclusive Economic Zone, lacking the legal authority to undertake such activities in this area.'

The Chinese embassy in the Philippines has not yet commented on the incident.

The Philippines is currently embroiled in a territorial dispute with China over parts of the South China Sea.

Expansionist China currently lays claim over almost the entire South China Sea, one of the world's busiest sea lanes. But a United Nations-backed tribunal in 2016 deemed its claims groundless.

The Communist rogue state - accused of genocide for its crimes against the Uyghur population - has been steadily increasing its influence in recent years through investment in developing countries.