China has been accused of contaminating contested waters in the South China Sea with cyanide, according to allegations from the Philippines. The Philippine government claims that this activity has been ongoing since 2025 and that its military has confiscated bottles containing cyanide from Chinese fishing vessels operating in the region.
In response to these allegations, Beijing dismissed the claims as a “farce.” The Philippines characterized the actions as “sabotage,” asserting that China is deliberately polluting the waters around Second Thomas Shoal in the Spratly Islands, a location crucial for shipping and believed to be rich in natural resources.
Cornelio Valencia, assistant director-general of the Philippines’ National Security Council, stated at a news briefing that the use of cyanide at Ayungin Shoal poses a significant threat to local fish populations, which are a vital food source for the Philippine Navy. He emphasized that this poisoning endangers naval personnel through exposure to contaminated waters and the consumption of tainted fish, while also damaging coral reefs.
The Chinese foreign ministry responded to these accusations, calling them “completely unbelievable” and unworthy of serious consideration. Spokesman Guo Jiakun accused the Philippines of illegally harassing Chinese fishermen who were merely carrying out standard fishing operations.
Historically, Manila and Beijing have been embroiled in numerous maritime territorial disputes in this highly contested region. Notably, a violent encounter in June 2024 involved Chinese coast guard personnel attacking Philippine Navy vessels with knives and sticks.
China asserts extensive claims over the South China Sea, despite an international tribunal ruling that these claims lack legal validity. Valencia mentioned that the Philippines had previously raised concerns about the alleged poisoning during a meeting with Chinese officials, but no formal response had been received.
He also warned that the damage to the reef from cyanide could threaten the stability of the BRP Sierra Madre, a World War II-era ship that the Philippines deliberately grounded in 1999 to assert its claim over the territory.
Rear Admiral Roy Vincent Trinidad from the Philippine Navy reported that troops had recovered ten bottles of cyanide from Chinese fishing boats in February, July, and October of 2025. He noted that naval personnel had witnessed another incident where Chinese fishermen were seen poisoning the waters near the shoal last month, with subsequent tests confirming the presence of cyanide in the water.
Fortunately, no personnel aboard the BRP Sierra Madre have tested positive for the toxin. Both Valencia and Trinidad suggested that the fishing vessels were operating under the auspices of the Chinese Navy. Valencia mentioned that the National Security Council intends to submit a detailed report to the Philippine foreign ministry next week, which could potentially serve as the foundation for a diplomatic protest.
In light of these developments, Manila has instructed its navy and coast guard to enhance patrols in the area to mitigate further environmental damage.
