A Philippine helicopter followed a China Coast Guard (CCG) monster ship lurking off the coast.

Footage shows the Philippine Coast Guard (PCG) Islander helicopter issuing a radio challenge to CCG vessel 5901 sailing near the shores of Zambales province on January 13.

The aircraft was deployed to monitor the Chinese vessel's movements after the PCG's BRP Teresa Magbanua stationed in the area returned to the Port of Bataan for repairs due to overheating.

In a statement on Monday, PCG spokesman Commodore Jay Tarriela said: 'This afternoon, the PCG Islander asserted a firm position against the illegal presence of the Chinese monster ship within the Philippines' Exclusive Economic Zone (EEZ) by issuing a radio challenge.

'This emphasised that the Chinese Coast Guard vessel is operating within Philippine maritime jurisdiction and that China lacks the legal authority to claim it is conducting legitimate maritime patrol operations. The Chinese vessel was tracked at an approximate distance of 67 nautical miles off the coast of Zambales.'

The National Maritime Council said the Philippine government has filed a diplomatic protest over the 'illegal presence' and 'provocative actions' of the China Coast Guard.

The massive CCG 5901, the world's largest coast guard vessel at 541 feet and 12,000 tons, started lurking off the seaside province on January 4 afternoon. Another CCG ship had headed to the area to replace it on January 8, before it circled back to the area, officials said.

Authorities believe it was deployed to intimidate Filipino fishermen from entering the Scarborough Shoal, a disputed fishing ground and resource-rich area in 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.