China warns foreign spies are using spy turtles and fish with sensors to map its coastline

China's Ministry of State Security warned on Friday that foreign intelligence agencies are fitting turtles and fish with sensors to collect sensitive marine data and map the country's coastline.

Beijing did not name a specific country but framed the warning as a threat from Western competitors. The ministry posted the alert on social media under the title "Under the deep blue, undercurrents are surging."

What are China's spy turtles and how do they work?

According to the ministry, foreign spies attach sensors to relatively large marine animals and release them in specific coastal waters. The animals then collect data on water temperature, salinity and ocean currents, transmitting the information overseas via satellite. The ministry labelled a dedicated section of its post "spy turtles, spy fish."

The data gathered from these animals, the ministry said, is used to build "underwater maps" of China's coast. Those maps can identify weak points in coastal defences, posing what Beijing described as a serious threat to national security. The ministry offered no independent verification of the claims or details of when or where the animals were found.

What other espionage devices did China say it discovered?

Beyond marine animals, the ministry said foreign groups had deployed solar-powered wave gliders, buoys fitted with high-precision sensors, and devices installed on cargo ships capable of capturing port activity in real time. All of these, it said, were designed to collect sensitive maritime intelligence without detection.

The ministry urged organisations to conduct proper security checks on equipment received from abroad. It also called on fishers to report any suspicious buoys or devices found at sea. No specific foreign agency was named in connection with any of the alleged methods.

How does this fit into China's broader espionage warnings?

Beijing and Western governments have long traded accusations of spying. Last year, China warned government workers to stay alert to honeytrap recruitment schemes, after a public servant was reportedly lured by a foreign agent.

This month, the Five Eyes alliance of Western security agencies said Chinese spies were posing as online job recruiters to extract sensitive information from targets abroad.