Tensions are rising in the South China Sea, with Philippine authorities claiming China’s coast guard and navy have harassed them with “aggressive manoeuvres”.

Vessels from the Philippine Bureau of Fisheries and Aquatic Resources (BFAR) were undertaking a scientific survey in Sandy Cay with the aim of sampling sand last Friday, January 24, the Philippine Coast Guard (PCG) said in a statement on Saturday.

However, “aggressive manoeuvres” from deployed Chinese authorities forced the marine survey to be suspended, they went on to claim. 

The PCG said: “During the mission, the BFAR vessels encountered aggressive maneuvers from three Chinese Coast Guard vessels 4106, 5103 and 4202.” 

They also claimed the incident is a “blatant disregard” of the 1972 Convention on the International Regulations for Preventing Collisions at Sea (COLREGs).

The Philippine Coast Guard said four smaller boats were also deployed by the China Coast Guard (CCG), which harassed two of the Philippine bureau’s inflatable boats. 

Sandy Cay, where the survey took place, is a group of low reefs located 3.7 kilometers from Thitu Island which is occupied by the Philippines - it is locally known as Pag-asa island.

“Compounding the situation, a People’s Liberation Army-Navy (PLAN) helicopter, identified by tail number 24, hovered at an unsafe altitude above the BFAR RHIBs, creating hazardous conditions due to the propeller wash,” the Philippine Coast Guard said.

However, the China Coast Guard has since released a statement claiming it expelled the Philippine vessels for unlawfully intruding into its waters.

China claims to have “indisputable sovereignty” over the disputed waters in the South China Sea, promising to continue to protect its maritime rights and interests, China Coast Guard spokesperson Liu Dejun said on Saturday.

Following the incident last week, the Philippine authorities have said the maritime operation has been suspended, according to the Philippine Coast Guard. The country’s foreign affairs department is now expected to file a diplomatic protest against China over the encounter, said Foreign Affairs Undersecretary Eduardo De Vega.