Anyone can be a target, no matter how junior, the email adds, with “common covers” including “diplomats, journalists, lobbyists, scientists or PhD students.”

Belgian security officials estimate that, in some embassies, between 10 and 20 percent of the diplomats are intelligence officers, while as many as one in five of the Chinese journalists working in Brussels are suspected to be intelligence officers.

The EU’s diplomatic service cautioned its staff about the threat of Russian and Chinese espionage back in 2019, warning there were hundreds of spies from Beijing and Moscow slinking around the Belgian capital and eavesdropping on conversations at bars and restaurants near the Commission’s headquarters.

A sweeping review of the bloc’s readiness for war and crisis last month recommended the EU establish its own intelligence agency to help countries fend off threats, saboteurs and foreign agents.

The suggestion follows warnings from Western intelligence agencies and spy chiefs around the bloc that the threat of Russian espionage has increased since the Kremlin’s full-scale invasion of Ukraine began in early 2022.