The Philippines said a huge Chinese coast guard ship widely known as the “Monster” has returned to its exclusive economic zone in the South China Sea, prompting its own coast guard vessel to approach and issue a radio challenge.

The China Coast Guard vessel 5901 has replaced another Chinese vessel within the Philippines’ exclusive economic zone and positioned 97 nautical miles off the coast of Zambales.

China has accused the Philippines of repeated encroachment in its waters. China with its largest navy in the world claims most of the South China Sea, a key conduit for $3 trillion of annual ship-borne trade, as its own territory, with a massive coast guard presence in and around the EEZs of neighbours Vietnam, the Philippines, and Malaysia.

The Philippines has accused a giant Chinese coast guard vessel it dubbed as the “Monster” of maintaining an “illegal presence” in its exclusive economic zone as Beijing ramps up activities in the disputed South China Sea.

China’s increasing presence in the South China Sea has sparked concern among neighboring nations. Last month, Beijing conducted large-scale military drills near Scarborough Shoa

A Chinese navy helicopter hovered over a Philippine Coast Guard (PCG) vessel as China's monster ship lingered in Philippine waters. Footage shows the People's Liberation Army-Navy (PLA-N) aircraft with tail number 47 circling above the PCG BRP Cabra monitoring the gargantuan China Coast Guard (CCG) vessel 5901 some 70 nautical miles off Zambales province on January 7.

The PCG has been monitoring the "monster ship" since last Saturday, when it was spotted by the Dark Vessel Detection system 54 nautical miles off Capones Island in Zambales.