The Philippine Coast Guard on Friday issued a radio challenge against a China Coast Guard vessel off the coast of Zambales in the West Philippine Sea.

A Philippine Coast Guard patrol ship issued a radio challenge to Chinese vessels off Zambales province due to their illegal presence in the West Philippine Sea.

China's largest Coast Guard vessel has begun to sail away from the waters off Zambales after loitering there for four days, only to be replaced by another Chinese ship in what authorities call a calculated move to maintain Beijing's illegal presence in the area.

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.

A Coast Guard vessel has continued to challenge the presence of Chinese ships “exhibiting erratic movements” in waters off Zambales.

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.

Malacaang expresses "grave concern" over the presence of China's so-called monster ship off the coast of Zambales, adding that the Philippines is actively challenging its presence.