The Philippine Coast Guard said Chinese vessels fired three flares toward its patrol plane conducting a routine flight in the disputed South China Sea on Dec. 6, the latest incident in a pattern of aggressive Chinese behaviors aimed at asserting its territorial claims in the region.

Jay Tarriela, Philippine Coast Guard spokesperson for the South China Sea, said in an X post that the Philippine aircraft took off from a local airport on the morning of Dec. 6 for a maritime domain awareness flight over the Kalayaan Island Group in the Spratly Islands.

Tarriela said the flight was part of his country’s mandate to monitor the marine environment, evaluate the state of fish stocks, and assess the well-being of Filipino fishermen in the region.

The flight was a collaboration between the Philippine Coast Guard and Manila’s Bureau of Fisheries and Aquatic Resources, according to Tarriela.

“The [Bureau of Fisheries and Aquatic Resources] aircraft recorded video footage of three (3) flares fired from the reef toward the aircraft during its lawful overflight,” Tarriela stated.

The flares were fired from the Chinese-occupied Subi Reef, known as Zamora Reef in the Philippines, he said.

Subi is among seven contested, largely submerged reefs that the Chinese regime has transformed into island bases in the Spratly Islands, the most disputed region of the South China Sea. According to U.S. and Philippine security officials, these man-made islands are protected by a missile system, and three of them host military-grade runways.

The Philippine patrol plane also spotted a Chinese vessel belonging to the People’s Liberation Army Navy that was located about 14 nautical miles northwest of Sabina Shoal, known as Escoda Shoal in the Philippines, an uninhabited and contested feature.

“This vessel repeatedly issued radio challenges against the BFAR aircraft while it was flying well within Philippine sovereign rights,” Tarriela stated.

The flight is conducted in accordance with international regulations, including the 2016 arbitration ruling issued by the Permanent Court of Arbitration in The Hague, he said.

The 2016 ruling rejected China’s “nine-dash line” claim to about 85 percent of the South China Sea’s 2.2 million square miles, saying that Beijing’s assertion was inconsistent with the U.N. Convention on the Law of the Sea.

It was the Philippines that initiated the arbitration proceedings against China in 2013, leading to the 2016 ruling.

Beijing, which has dismissed the 2016 ruling, did not immediately comment on the incident.

China also fired flares from Subi Reef at a Philippine aircraft conducting a routine patrol in August 2024. Two days before the incident, a Chinese fighter jet also fired multiple flares at the same Philippine aircraft “at a dangerously close distance of approximately 15 meters [about 49 feet].”

The two incidents in 2024 drew condemnation from the United States. In a statement posted on X at the time, U.S. Ambassador to the Philippines MaryKay Carlson urged China to “cease provocative and dangerous actions that undermine” the Indo-Pacific.

In October, Australia also expressed concerns after a Chinese jet released flares in close proximity to an Australian maritime patrol plane carrying out surveillance in the South China Sea. In a statement, the Australian defense ministry called China’s action “unsafe and unprofessional.”

“Australia expects all countries, including China, to operate their militaries in a safe and professional manner,” the Australian defense ministry stated.

The Associated Press contributed to this report.