Chinese coast guard vessels blocked a Philippine interagency team pursuing a foreign fishing boat suspected of dynamite fishing near Pag-asa Island in the South China Sea on Sunday, forcing personnel to abandon the operation over safety concerns, the Philippine Coast Guard (PCG) said.

Commodore Jay Tristan Tarriela, PCG spokesman, said personnel from the PCG, the Philippine Navy and the Philippine National Police (PNP) Maritime Group responded to a report of suspected blast fishing near Sandy Cays 2 and 3, about three nautical miles (5.56 kilometers) west of Pag-asa Island, also known internationally as Thitu Island. Pag-asa is the largest maritime feature occupied by the Philippines in the Kalayaan Island Group, Manila's term for its holdings in the disputed Spratly archipelago, and its surrounding reefs have long supported Filipino fishing crews. Blast fishing uses explosives to stun and kill fish, shattering coral reef habitat that can take decades to recover.

The Philippine team departed Pag-asa Island aboard several small boats at 9:50 a.m. Minutes later, China Coast Guard (CCG) vessels 5102 and 21581 moved toward their path, sounding their horns and issuing radio challenges, Mr. Tarriela said in a Facebook post. The cays sit well inside the waters the PCG treats as Philippine territorial sea — under the United Nations Convention on the Law of the Sea, a coastal state may claim up to 12 nautical miles from its coast — in an area where Beijing's own claims overlap Manila's.

The team reached the suspected fishing vessel at about 10 a.m. and ordered it to stop, but the boat allegedly ignored the instructions and headed southwest toward Zamora (Subi) Reef, a Chinese-occupied feature that Beijing has built into one of its largest artificial-island outposts in the Spratlys. During the pursuit, CCG vessel 21581 shadowed and blocked the Philippine boats, at one point coming within about 10 yards of a PCG high-speed response boat, according to Mr. Tarriela.

A People's Liberation Army Navy helicopter also circled the Philippine team four times at about 10:13 a.m. — conduct Mr. Tarriela described as an "unnecessary act of intimidation."

The team abandoned the chase at about 10:23 a.m. for safety reasons and returned to Pag-asa Island at 10:48 a.m. No casualties were reported.

Mr. Tarriela characterized the operation as a "routine law enforcement operation" against destructive fishing that "was not directed at any country." He accused the Chinese coast guard of allowing the suspected violator to escape, adding that it had no law enforcement authority in Philippine territorial waters around Pag-asa Island.

"The CCG did not protect the marine environment," he said. "It made it easier for a suspected violator to escape."

He also rejected claims that Chinese personnel had expelled Philippine vessels or handled the situation. "The PCG, together with the Philippine Navy and the PNP Maritime Group, will continue to enforce Philippine laws and protect the marine resources around Pag-asa Island and the Kalayaan Island Group," he said. The back-and-forth illustrates how quickly patrol-level encounters in the archipelago can shift from coast guard matters to diplomatic ones.

The incident will be documented and referred to the Department of Foreign Affairs for appropriate action through existing channels, he added. Whether the referral produces a formal protest will be the next concrete indicator of how Manila chooses to respond.

The Chinese Embassy in Manila did not immediately reply to a Viber message seeking comment.

Meanwhile, the National Maritime Council on Sunday urged China to stop "illegal and unauthorized activities" by its vessels within the Philippine exclusive economic zone (EEZ). The council commended the PCG for responding to the Chinese research vessel JIA HAI KE 7, which was spotted about 37 nautical miles northwest of Itbayat, Batanes, within the Philippine EEZ. An EEZ extends up to 200 nautical miles from a state's coast under UNCLOS, giving the coastal state sovereign rights over the resources and scientific activity within it.

The council said the incidents underscored the importance of sustained maritime monitoring and coordination among government agencies, stressing that protecting Philippine maritime rights "does not require unnecessary confrontation." It also urged China to comply with its obligations under the United Nations Convention on the Law of the Sea, citing the 2016 arbitral ruling that upheld Philippine sovereign rights and jurisdiction over marine scientific research within its EEZ. That award, issued by a tribunal in The Hague in a case brought by Manila, found no legal basis for Beijing's sweeping South China Sea claims; China rejected it and the convention offers no mechanism to enforce it.

— Pexcel John Bacon