MANILA, Philippines (AP) — Chinese coast guard ships maneuvered dangerously close to Philippine coast guard ships at least four times near a disputed shoal over the past year, in moves that increased the risk of collision and violated international safety regulations, the Philippine government said Sunday.

It was not immediately clear if the Philippines has formally protested the aggressive actions by the Chinese ships, but Manila’s coast guard said the incidents would not deter it from deploying patrol vessels at Scarborough Shoal and in other areas within the country’s internationally recognized exclusive economic zone.

China seized Scarborough Shoal, a rich fishing area about 200 kilometers (120 miles) off the northwestern coast of the Philippines and 600 kilometers (370 miles) southeast of China, after a tense naval standoff in 2012. Chinese coast guards ships then surrounded the shoal and restricted Filipino fishermen’s access.

The U.S. has accused China of bullying smaller South China Sea claimants like the Philippines and has deployed Navy ships and aircraft to promote freedom of navigation and overflight in the region. China, which claims the South China Sea virtually in totality, has warned Washington to stay away and accused it of meddling in what it says is a purely Asian dispute.

The incidents were reported to the Department of Foreign Affairs in Manila and an inter-agency body on the South China Sea “to address this issue through rules-based and peaceful approaches,” Philippine coast guard chief Adm. Artemio Abu said in a statement.

Earlier this month, a Chinese coast guard ship maneuvered just 21 yards (63 feet) from a Philippine patrol vessel and restricted its maneuvering space in the vicinity of Scarborough Shoal, the Philippine coast guard said, adding that the Chinese action was “a clear violation” of a 1972 international safety regulation that aims to prevent sea collisions.

In June last year, two Chinese coast guard ships on two successive days moved dangerously close to two Philippine coast guard ships, which were participating in a maritime exercise off Scarborough Shoal. A month before, a Chinese coast guard ship moved close to a Philippine Bureau of Fisheries vessel manned by coast guard personnel also near the shoal, according to the coast guard.

There was no immediate comment from the Chinese Embassy in Manila.

China’s seizure of Scarborough Shoal prompted the Philippines to bring the disputes to international arbitration. In 2016, a U.N.-backed tribunal invalidated most of China’s claims and said it has violated the rights of Filipinos to fish at the shoal.

China dismissed the ruling as a sham and continues to defy it but allowed Filipino fishermen to return to the shoal under Philippine President Rodrigo Duterte, who nurtured closer ties with Beijing after taking office in 2016. Despite cozier relations, however, sporadic territorial spats have persisted.

Vietnam, Malaysia, Taiwan and Brunei also lay claims to the busy waterway through which an estimated $5 trillion in global trade passes each year.

“We are fully aware of dangerous situations at sea, but these will not stop our deployment of assets and personnel” to serve Filipino fishermen, Abu said. “As long as they feel safe seeing us during their fishing operations, we know that we are doing our job well.”

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