The China Coast Guard (CCG) blocked, shadowed, and intercepted the automatic identification system (AIS) signal of a Bureau of Fisheries and Aquatic Resources (BFAR) vessel in Bajo de Masinloc (Panatag or Scarborough Shoal) in Zambales, the Philippine Coast Guard (PCG) disclosed on Sunday, February 25.

The incident occurred last Thursday, February 22, during the conduct of the rotational deployment of the PCG and BFAR in Bajo de Masinloc, according to PCG spokesperson for West Philippine Sea Commodore Jay Tarriela.

BFAR multi-mission offshore vessel BRP Datu Sanday (MMOV-3302) departed Capinpin Port in Orion, Bataan on February 21 to distribute fuel and grocery packs to Filipino fishermen and hold patrol operations in Bajo de Masinloc.

Around 6:34 a.m. on February 22, China Coast Guard (CCG) vessel with bow number "3105" started shadowing BRP Datu Sanday at approximately 24.15 nautical miles southeast of Bajo de Masinloc, Tarriela said. An unidentified warship was also observed to be accompanying the CCG ship.

While BRP Datu Sanday was sailing closer to Bajo de Masinloc, the CCG deployed rigid-hull inflatable boats (RHIBs) "3065" and "3302-1" to lay down a floating barrier, a technique that they frequently use to block foreign vessel from accessing the shoal.

Tarriela said that the CCG then started blocking the AIS signal of BRP Datu Sanday around 8:05 a.m. "to support China's press release of successful 'repelling' of Philippine state vessels in [Bajo de Masinloc]." 

Shortly after that, the CCG released a statement via their official website that they have repelled a Philippine vessel that allegedly intruded into the waters adjacent to Huangyan Dao, the name they call Bajo de Masinloc.

The AIS is an important factor in safe sea maneuvering as it transmits a vessel's position so that other ships are aware of its location. 

Blinding a ship by blocking its AIS signal poses several risks including possible grounding or collision.

"Regarding AIS signal jamming, we noticed that even if our AIS are turned on, there are instances that our vessels cannot transmit their AIS signal," Tarriela said.

But this was not the first time that the CCG allegedly blocked a Philippine vessel's AIS signal, according to Tarriela.

"We also noticed this occurrence during the last deployment of BRP Teresa Magbanua and BRP Datu Tamblot," he said.

"We assume that they do the jamming every time they released their statements that they repelled our vessels. Through such jamming, any commercial AIS monitoring cannot also disprove such statement because they may not be able to find our vessels," he explained.

'Continued harassment'

After blinding BRP Datu Sanday, CCG 3105 started corralling, shadowing, and conducting dangerous maneuvers towards BRP Datu Sanday along with Chinese maritime militia vessels "00107" and "00309" as the BFAR vessel approached the anchorage area of Filipino fishing boats at approximately 1.5 nautical miles south, southwest off Bajo de Masinloc, according to Tarriela.

Watch: BFAR vessel blocked, 'blinded' by China Coast Guard in Bajo de Masinloc -- PCG

The harassment, however, did not stop BRP Datu Sanday as it successfully reached the Filipino fishermen who were waiting for the fuel assistance. 

BRP Datu Sanday distributed fuel and groceries to a total of 44 Filipino fishing boats, enabling them to last longer at sea and catch more fish.

Tensions rose when the CCG 3105 deployed a RHIB which approached Filipino fishing boat "Subic". BRP Datu Sanday responded by dispatching a rubber boat with BFAR personnel onboard to document the Chinese boat and escort the Filipino fishermen.

Chinese aircraft in PH airspace

Tarriela revealed that PLA Navy warship "175" also approached the port beam of BRP Datu Sanday at a close distance of 10 nautical miles while the BFAR vessel was preparing to leave Bajo de Masinloc on Friday, February 23.

The PLA Navy 175 then did a daring act when it launched a helicopter with tail number "68" which "did aerial surveys passing by from northwest to east off Bajo de Masinloc."

"We observed that one of their gray hulls deployed a PLA Navy helicopter which conducted patrols in the territorial airspace while we distributed the fuel subsidy to the Filipino [fishing boats]," Tarriela said.

All throughout the mission, Tarriela said that there were three PLA Navy warships, four CCG vessels, seven maritime militia boats, a drone, and a PLA Navy helicopter that were monitored in Bajo de Masinloc against a singular BFAR vessel that was the BRP Datu Sanday.

A total of 28 radio challenges were also issued by the CCG but Tarriela said the BRP Datu Sanday promptly responded to all of them.