Philippines Accuses China of Using Cyanide to Poison South China Sea Atoll

The Philippines has accused Chinese fishermen of dumping cyanide in waters around Second Thomas Shoal in the disputed Spratly Islands, alleging the poisoning began last year and is intended to kill fish populations that feed Filipino troops stationed on the grounded warship BRP Sierra Madre. Philippine Navy spokesman Roy Vincent Trinidad reported that troops seized 10 bottles of cyanide from sampan boats in February, July and October, with water samples testing positive for the poison. China's foreign ministry spokesman Guo Jiakin dismissed the allegations as a farce that is not worth refuting, while Manila has raised the issue diplomatically and ordered increased patrols. The incident escalates tensions in the South China Sea, where overlapping territorial claims involve China, the Philippines, Vietnam, Taiwan, Malaysia and Brunei, and where more than half the world's fishing vessels operate in waters home to potential energy reserves.

Philippine Accusations of Cyanide Poisoning by Chinese Fishermen

• ▪The Philippine navy and coastguard have been ordered to increase patrols around Second Thomas Shoal
• ▪The Philippine National Security Council said the alleged cyanide poisoning began in 2025 around Second Thomas Shoal
• ▪Philippine National Security Council assistant director-general Cornelio Valencia said the use of cyanide posed health risks to troops by contaminating water and fish
• ▪The Philippines accused Chinese fishermen of dumping cyanide in waters around the Spratly Islands in the South China Sea
• ▪Manila raised the alleged cyanide poisoning with Beijing at a recent meeting but received no formal response
• ▪Cornelio Valencia said cyanide use could damage coral reefs that help support the BRP Sierra Madre's structural foundations
• ▪Cyanide fishing is illegal under Philippine law and widely banned across Southeast Asia because of its destructive impact on marine ecosystems
• ▪Philippine Navy spokesman Rear Adm Roy Vincent Trinidad said Filipino troops seized 10 bottles of cyanide from sampan boats allegedly launched from Chinese fishing vessels in February, July and October of last year

Strategic Importance of Second Thomas Shoal and BRP Sierra Madre

• ▪Second Thomas Shoal is home to a small Philippine military outpost aboard the BRP Sierra Madre
• ▪The BRP Sierra Madre is a rusting World War Two-era ship deliberately grounded at Second Thomas Shoal in 1999 to assert Manila's claim to the territory
• ▪Second Thomas Shoal is part of the Spratly archipelago in the South China Sea

Broader South China Sea Territorial Disputes and Military Alliances

• ▪The Philippines signed a military deal with France in March that will see Paris send a contingent of 15 to 20 troops to join the Balikatan exercises on 20 April
• ▪China claims the South China Sea nearly in its entirety, despite a 2016 international tribunal ruling that found China's sweeping claim had no legal basis
• ▪Scarborough Shoal is a little more than 100 miles from the Philippines and 500 miles from China
• ▪Beijing rejected the 2016 international tribunal ruling on the South China Sea
• ▪The Philippines invokes its geographical proximity to the Spratly Islands as the main basis of its claim for part of the grouping