The Philippines accused Chinese fishermen on Monday of dumping cyanide in disputed waters of the South China Sea.
The alleged dumping took place near Second Thomas Shoal, locally known as Ayungin Shoal, a long-contested reef where Philippine forces are stationed aboard the BRP Sierra Madre.
“The use of cyanide on Ayungin Shoal is a term of sabotage that seeks to kill local fish populations, depriving Navy personnel of a vital food source,” National Security Council (NSC) assistant director-general Cornelio Valencia told reporters.
“These actions also ‘threaten our Navy personnel’ through exposure to contaminated water, eating poisoned fish, as well as eroding corals,” he added.
Authorities said Philippine forces recovered multiple bottles of the toxic substance from small boats launched from Chinese fishing vessels.
Philippine Navy spokesman Rear Admiral Roy Vincent Trinidad said troops seized 10 bottles of cyanide during operations in February, July and October 2025. Subsequent testing confirmed the presence of cyanide.
Trinidad added that none of the Filipino troops aboard the warship have tested positive for exposure to the poison.
The South China Sea remains one of Asia’s most volatile maritime flashpoints, with overlapping territorial claims between China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan. Beijing claims nearly the entire waterway, despite a 2016 international arbitration ruling that found its sweeping claims had no legal basis.
Tensions between Manila and Beijing have repeatedly escalated in recent years, including violent confrontations involving coast guard vessels.
In a statement carried by Reuters, China’s Foreign Ministry denied wrongdoing and called the accusations a “stunt.”
“The Philippine side illegally harassed the Chinese fishing boats conducting normal fishing, grabbed the fishermen’s living supplies, and staged this so-called cyanide stunt. There is no credibility whatsoever to their story,” foreign ministry spokesperson Guo Jiakun said on Monday.
Philippine officials said the NSC is preparing a formal report to be submitted to the Department of Foreign Affairs, which could serve as the basis for a diplomatic protest. Manila has also ordered increased naval and coast guard patrols in the area, citing the need to prevent further environmental harm and protect personnel stationed at the shoal.
