MANILA – The Philippines has confirmed that Chinese boats used in 2025 cyanide that threatens the stability of its military outpost in the disputed South China Sea, as well as the safety of its soldiers.

The Philippines’ National Security Council said at a news briefing that laboratory analysis confirmed that bottles recovered from Chinese boats near Second Thomas Shoal in February and October 2025 contained cyanide.

The council said the use of the highly toxic chemical “is a form of sabotage” that “compromise” the stability of BRP Sierra Madre, a World War II-era ship that’s been grounded in contested waters for more than two decades and now serves as a Philippine military outpost.

Cyanide could also kill fish around the shoal, depriving soldiers of a food source, it added.

“These laboratory findings remove any doubt as to the dangerous and unlawful nature of these activities,” council spokesman Cornelio Valencia Jr said. “The deliberate use of cyanide raises serious concerns on the illegal and destructive practices and threaten our navy personnel.”

Patrols around the disputed shoal may also be intensified, Mr Valencia said.

The council will relay its findings to the Department of Foreign Affairs for a possible diplomatic protest, he said.

Manila and Beijing are locked in a territorial dispute in the South China Sea, a resource-rich waterway and a critical trade route.

In 2024, the two nations forged a provisional agreement on the Philippines’ missions to its military outpost at Second Thomas Shoal to ease tensions.

Those operations by Manila – aimed at resupplying provisions and rotat...