A China Coast Guard ship reportedly tailed Filipino researchers conducting a survey in contested waters in the South China Sea.

China Coast Guard vessel 5303 allegedly stalked the Philippine research vessel BRP Hydrographer Ventura and its escort BRP Gabriela Silang that were conducting a hydrographic survey in the Scarborough Shoal, around 110 nautical miles off the Philippines' Bolinao town in Pangasinan province on April 14.

In a press conference on April 15, Assistant Director General Jonathan Malaya, spokesman for the National Security Council, said: 'What China is doing is shadowing. There is no interference, there is no standoff, there is nothing.

'It is just a normal day at the West Philippine Sea.'

Philippine Coast Guard (PCG) spokesman Commodore Jay Tarriela said in a statement: 'Although they have not directly obstructed or interfered with our survey activities, this relentless behavior serves as undeniable evidence that the People's Republic of China (PRC) is unhesitant in deploying its vessels within our Exclusive Economic Zone to intimidate and impede our legitimate operations, specifically in the field of marine scientific research.'

The alleged shadowing incident comes almost a month after a Communist Chinese helicopter appeared to harass Filipino scientists doing research on the Sandy Cay sandbars in the South China Sea on March 23.

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.