On Wednesday, the Philippines reported that a Chinese navy helicopter shadowed and approached one of its fisheries bureau aircraft during a patrol near the contested Scarborough Shoal, marking another confrontation between the two nations embroiled in a longstanding territorial dispute.

The Philippine National Security Council (NSC) indicated that the incident occurred on Monday, but the aircraft successfully completed its mission. The Chinese embassy in Manila has yet to respond to inquiries regarding the matter.

This incident adds to a series of aerial and maritime encounters between the two countries, which have been at odds over various areas in the South China Sea, including the Scarborough Shoal, a highly disputed location that has been under the control of China’s coast guard for over ten years.

The NSC stated that China’s actions constituted a violation of air safety regulations. China asserts its claim over nearly the entire South China Sea, including the Scarborough Shoal, based on interpretations of historical maps, which is sought after for its rich fishing resources and picturesque lagoon.

The shoal, named after a British ship that became stranded there centuries ago, is situated 200 km (124 miles) from the Philippines, within its exclusive economic zone (EEZ). A ruling by the Permanent Court of Arbitration in 2016 determined that China’s extensive claims lacked support from international law, a verdict that Beijing has chosen to disregard. The tribunal did not address the issue of sovereignty over the Scarborough Shoal, noting instead that it serves as a traditional fishing area for multiple nations.

In a separate development, the Philippine defense minister urged China on Wednesday to withdraw its vessels from the EEZ and accused Beijing of attempting to interfere with the country’s defense operations, including the use of a U.S. mid-range missile system for training purposes. According to a report from Reuters last week, the United States has no immediate intentions to remove the missile system, which can be outfitted with cruise missiles capable of targeting Chinese locations.

“China claims to be alarmed, but that constitutes interference in our domestic matters,” Defense Secretary Gilberto Teodoro stated to the press. “Why don’t they set an example? They should dismantle their nuclear arsenal, eliminate all their ballistic missile capabilities, and withdraw from the West Philippine Sea and Mischief Reef,” he continued, referring to the Philippine EEZ and a manmade, militarized island constructed by China.

China has voiced concerns regarding the deployment of the Typhon system in the Philippines, accusing the United States of exacerbating an arms race. Philippine military chief Romeo Brawner expressed on Wednesday that if it were up to him, “I would prefer to have the Typhons stationed in the Philippines indefinitely.”