The Philippine Coast Guard (PCG) continued to tail a Chinese monster ship allegedly loitering in Philippine waters.

Footage shows the PCG vessel BRP Cabra (MRRV-4409) circling the mammoth China Coast Guard (CCG) ship CCG-5901 lurking off the Philippine island of Luzon on January 6.

In a statement on Monday, PCG spokesman Commodore Jay Tarriela said: 'Observations reveal that the CCG vessel's erratic movements indicate it is not engaged in innocent passage but rather asserts that it is conducting a law enforcement operation, claiming jurisdiction over these waters as belonging to the People's Republic of China.

'In response, the crew of BRP Cabra has remained steadfast in challenging this assertion, diligently tailing and shadowing CCG-5901 to uphold Philippine sovereign rights.'

The CCG-5901, the largest coast guard vessel in the world at 541 feet and 12,000 tons, was earlier seen sailing some 54 miles off Capones Island in Zambales province on January 4 afternoon. Local media reported it was last seen 80 nautical miles from Lubang Island in Occidental Mindoro province.

Authorities believe its presence was meant 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.