THE PHILIPPINES vowed on Tuesday not to back down in the face of a Chinese effort to block its fishermen from a fiercely contested shoal in the South China Sea, while Beijing warned the Southeast Asian nation not to “provoke and cause trouble.”

The comments came a day after Manila cut a 300-meter (980-ft) floating barrier installed by Beijing at the shoal, one of Asia’s most contested maritime features, making use of coastguard personnel posing as fishermen in a small boat.

The move, which the Philippines called a “special operation,” could further strain ties that have deteriorated this year.

“They might still return the floating barrier once again, they might still do shadowing and dangerous maneuvers once again,” Philippine coast guard spokesman Commodore Jay Tristan Tarriela told CNN Philippines.

Earlier, he said four Chinese vessels were in the area when a Philippine ship approached and were “not that aggressive,” adding it was clear media were on board the Philippine ship.

He said China’s coast guard had even removed remnants of severed buoy barriers and had been measured in its response to the presence of its vessel, which reached its closest point to the strategic atoll since China seized it in 2012.

“We have shown the world the Filipino people will not back down and we’re still going to consistently carry out whatever is necessary for us to maintain our presence,” Mr. Tarriela said.

The Scarborough Shoal, a prime fishing spot about 200 km (124 miles) off the Philippines and within its exclusive economic zone (EEZ), has been the site of decades of on-off disputes over sovereignty.

China, which calls the rocky outcrop Huangyan Island, has accused the Philippines of “intruding” in Chinese waters. On Tuesday, it warned Manila to steer clear of provocations.

“China firmly upholds the sovereignty and maritime rights of Huangyan Island, and we advise the Philippine side not to provoke and cause trouble,” Foreign Ministry spokesperson Wang Wenbin told a news briefing.

“China’s tired refrain of supposedly indisputable sovereignty and jurisdiction is totally contrived and not supported by historical evidence,” Jay L. Batongbacal, director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea, said in a Viber message.

“It has always been a mere paper claim that China never acted on until 1994, compared with the Philippines’ own exercise of administration and jurisdiction over the shoal since the Spanish and American periods,” he added.

The Philippines and China have repeatedly sparred over the shoal, but tension had ebbed under the previous pro-China administration in Manila.

Ties have soured this year, however, as new President Ferdinand R. Marcos, Jr., who authorized the cutting of the cordon, seeks to strengthen relations with ally the United States.

Such efforts included giving the US expanded military access to Philippine bases, a move criticized by China as provocative and liable to stoke regional tension.

Vessels of the two countries have faced off several times this year elsewhere in Philippine EEZ.

Manila has accused Beijing’s coast guard of dangerous and aggressive acts such as using a military-grade laser to deter a resupply mission to troops stationed on a rusty, grounded warship.

China says that occupation is illegal.

On Monday, Chinese nationalist tabloid the Global Times quoted an expert as saying Philippine decision-makers were acting under the influence of a United States bent on instigating conflicts to contain Beijing.

Control of the shoal, about 850 kms off mainland China, is a sensitive issue for Beijing, which for the past decade has maintained a constant presence of coast guard ships and fishing vessels there.

The shoal figured in a case the Philippines took to the Permanent Court of Arbitration in the Hague, which ruled in 2016 that China’s claim to most of the South China Sea had no basis under international law.

China does not recognize the ruling.

The Philippines’ Department of Foreign Affairs (DFA) would file a diplomatic protest against China in connection with the barrier, its top envoy Enrique A. Manalo told a Senate hearing on the agency’s budget.

He said that removing the barrier is within the Philippines’ territorial rights under international law. He also said the country aims to manage differences with China peacefully.

“Our aim is to manage disputes peacefully, and through the rule of law and international law,” he said. “We have a complex and big relationship with China.

Political analysts said China would likely keep its sea dispute with the Philippines away from a regional level to avoid a war that could involve the US, which would be too costly for its sluggish economy.

China’s Foreign Ministry on Monday accused the Philippines of entering the shoal on Sept. 22 “without their permission.”

Foreign Ministry spokesman Wang Wenbin said the installation of the barrier, which prevented Filipino fisherfolk from fishing in the area, was “professional and restrained.” He said the shoal, which is within the Philippines’ exclusive economic zone, “has always been China’s territory.”

Mr. Wang said China has “indisputable sovereignty” over the shoal, which the Philippines calls Bajo de Masinloc.

China’s admission it had installed the barrier means it is willing to “impose heavier costs all the more against the Philippines,” said Joshua Bernard B. Espeña, a resident fellow at the Manila-based think tank International Development and Security Cooperation.

“It signals China’s willingness to raise the escalatory ladder based on its core interest of claiming its so-called indisputable sovereignty in its fictitious 10-dash Line,” he said in a Facebook Messenger chat. “This cements the idea that China will be relentless as a rising great power.”

The Philippine Coast Guard (PCG) on Monday night said that upon Mr. Marcos’ order, it had executed a special operation to remove the barrier, which was first reported to the public on Sunday.

The barrier “posed a hazard to navigation” and hindered livelihood activities of Filipino fishermen at the shoal, which is “an integral part of the Philippine national territory,” Mr. Tarriela said.

Mr. Espeña said China’s aggressiveness is “actually doing the Philippines a favor” by bringing local elites and the public together “to forge a unified narrative” on defending Philippine territories in the South China Sea.

He said the Philippines deters Chinese aggression “by denial and punishment” and “should they fight us, we will conduct a strategy of attrition against them.”

“Imagine them spending a lot of resources just to achieve their objectives — this is too costly for the Chinese economy shifting gears from peacetime to wartime,” he said. “Moreover, we deter China by punishment because of the idea that due to the 2016 arbitral ruling, more and more countries are rallying behind the Philippines.”

He said China also fears being dragged into an unwanted war with the US, which has a 1950s Mutual Defense Treaty with the Philippines.

Philippine Solicitor General Menardo I. Guevarra on Monday said the government would consider suing China again before the Permanent Court of Arbitration (PCA) in the Hague because of the barriers. — Kyle Aristophere T. Atienza and John Victor D. Ordonez with Reuters