The Philippines has accused Chinese fishing vessels of deploying cyanide in the disputed waters of the Spratly Islands, alleging a deliberate attempt to sabotage the local ecosystem and jeopardize the health of Filipino military personnel. The accusations, detailed by the Philippine National Security Council (NSC), center on activities around the Second Thomas Shoal—a critical reef known to the Philippines as Ayungin Shoal—where tensions between Manila and Beijing have frequently escalated into physical confrontations.
This latest development marks a shift from traditional maritime skirmishes toward what Manila describes as environmental warfare. According to the NSC, the use of poison in these waters is intended to deplete fish populations, thereby stripping Philippine Navy personnel stationed at the shoal of a vital food source. Beyond the immediate impact on food security, officials warn that the chemical runoff threatens the structural integrity of the coral reefs and the safety of the troops through contaminated water and seafood.
The dispute over the South China Sea remains one of the world’s most volatile geopolitical flashpoints. Whereas Beijing claims nearly the entire waterway, an international ruling has previously determined that these assertions have no legal basis. The Philippines continues to assert its sovereign rights within its Exclusive Economic Zone (EEZ), which includes the Spratly chain and its mineral-rich waters.
A Pattern of Sabotage at Ayungin Shoal
The National Security Council alleges that the poisoning campaign began last year. Cornelio Valencia, assistant director-general of the NSC, characterized the use of cyanide as a “term of sabotage” during a news conference. He emphasized that the environmental damage extends beyond the loss of biodiversity, potentially eroding the very corals that provide the foundation for the region’s maritime features.
Of particular concern to Manila is the BRP Sierra Madre, a World War II-era warship that the Philippines deliberately grounded on the shoal in 1999 to establish a permanent presence. Valencia noted that the chemical degradation of the reef could compromise the structural foundations of the aging vessel, which serves as the primary outpost for Filipino troops in the area.
The Philippine Navy has provided specific evidence to support these claims. Rear Admiral Roy Vincent Trinidad, a Navy spokesperson, stated that troops seized 10 bottles of cyanide from small boats launched from larger Chinese fishing ships during encounters in February, July, and October 2025. Further evidence includes the direct observation of a Chinese sampan crew poisoning the waters last month, after which water samples from the shoal tested positive for cyanide.
Chronology of Reported Incidents
| Period | Event/Observation | Philippine Claim/Action |
|---|---|---|
| 2024 (General) | Onset of poisoning | NSC alleges cyanide use began around Second Thomas Shoal. |
| June 2024 | Violent Clash | Chinese coastguard personnel allegedly used knives and axes against Navy boats. |
| Feb, July, Oct 2025 | Seizures | Filipino troops seized 10 bottles of cyanide from Chinese-linked boats. |
| Recent Month | Direct Observation | Navy observed sampan crew poisoning water; samples tested positive. |
Beijing’s Response and the ‘Maritime Militia’
The Chinese government has dismissed the allegations with bluntness. During a regular news briefing on Monday, foreign ministry spokesman Guo Jiakun branded the accusations a “farce,” describing them as “completely unbelievable and not even worth refuting.”
Beijing countered by claiming that the Philippines has “illegally harassed” Chinese fishing vessels and robbed them of their supplies. This exchange highlights the enduring friction between the two nations, where “normal fishing activities” are often viewed by the opposing side as state-sponsored incursions. Both Rear Admiral Trinidad and Cornelio Valencia alleged that the “mother ships” supporting these fishing boats are actually operating on behalf of the Chinese Navy, a common characteristic of the so-called maritime militia.
This dynamic has led to a cycle of escalation. The June 2024 clash, in which Chinese personnel reportedly used knives and axes to board Philippine vessels, serves as a stark reminder of how quickly these territorial disputes can transition from diplomatic disagreements to violent encounters. The addition of chemical sabotage adds a new, more insidious layer to the conflict.
Environmental and Strategic Implications
The use of cyanide in coral reef environments is devastating. The chemical kills not only the target fish but too the polyps that build the reef, leading to rapid ecological collapse. For the Philippines, this is not merely an environmental tragedy but a strategic threat. The BRP Sierra Madre is an aging hull held together by the reef and the efforts of the soldiers aboard; any degradation of the seabed directly threatens the stability of the outpost.
The human cost is also a primary concern. While Rear Admiral Trinidad confirmed that none of the troops aboard the warship have tested positive for the poison so far, the risk of exposure through the food chain—specifically the consumption of poisoned fish—remains a critical vulnerability for the isolated garrison.
The Philippines is now moving toward a more formal diplomatic response. The NSC is preparing a detailed report for the Philippine foreign ministry, which is expected to serve as the foundation for an official diplomatic protest. In the interim, Manila has ordered the navy and coastguard to increase patrols to mitigate further environmental harm.
As the Philippines prepares its formal report next week, the international community continues to monitor the region for signs of further escalation. The next critical checkpoint will be the submission of the NSC report to the foreign ministry and any subsequent formal response from the Chinese embassy in Manila.
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