A floating barrier installed by China to prevent Filipino boats from fishing in a disputed area of the South China Sea has been removed, Philippine authorities said Monday, in the latest flashpoint between Manila and Beijing over their competing maritime claims.

Video released by the Philippine Coast Guard on Monday showed a Filipino diver cut what it said earlier was a 300-meter (984-feet) long string of buoys near Bajo de Masinloc, also known as Scarborough Shoal, a small but strategic reef and fertile fishing ground 130 miles (200 kilometers) west of the Philippine island of Luzon.

The footage showed the diver with a simple mask and snorkel slipping below the waves to use a small knife to cut through rope after reaching the barrier on a rickety fishing boat with a small crew.

The video is a vivid illustration of a fraught power struggle that has been playing out for years in the South China Sea as Manila tries to push back against increasingly assertive claims to the disputed strategic waterway by Beijing.

Philippine authorities claimed Sunday that three Chinese Coast Guard boats and a Chinese maritime militia service boat had installed the barrier following the arrival of a Philippine government vessel in the area.

“The barrier posed a hazard to navigation, a clear violation of international law,” the Philippine Coast Guard said in a statement Monday, adding that it also infringed on Philippine sovereignty.

In a regular press briefing Tuesday, Chinese foreign ministry spokesperson Wang Wenbin said “China is resolved in safeguarding its sovereignty and maritime interests over Huangyan Island,” referring to the disputed shoal by its Chinese name.

“We advise the Philippines not to make provocations or seek troubles,” he added.

Beijing claims “indisputable sovereignty” over almost all of the 1.3 million square miles of the South China Sea, as well as most of the islands and sandbars within it, including many features that are hundreds of miles away from China’s mainland.

Over the past two decades China has occupied a number of reefs and atolls across the South China Sea, building up military installations, including runways and ports, which have not only challenged the Philippines’ sovereignty and fishing rights but have also endangered marine biodiversity in the highly contested resource-rich waterway.

In 2016, an international tribunal in The Hague ruled in favor of the Philippines in a landmark maritime dispute, which concluded that China has no legal basis to claim historic rights to the bulk of the South China Sea.

Beijing has ignored the ruling.

Western marine security experts, along with officials from the Philippines and the United States, have increasingly accused Beijing of using ostensibly civilian fishing vessels as a maritime militia that acts as an unofficial – and officially deniable – force that China uses to push its territorial claims both in the South China Sea and beyond.

The situation comes days after the Philippine Coast Guard accused China’s maritime militia of turning vast patches of coral near the Palawan island chain into a bleached and broken wasteland.

China’s foreign ministry dismissed those allegations as “false and groundless.”