Security has been stepped up at a Nato airbase in Germany due to intelligence indicating a “potential threat”, the alliance said.
All staff not essential to missions have been sent home from Geilenkirchen air base, near the border with the Netherlands.
The site hosts the Airborne Warning and Control System, or Awacs, fleet, which function as Nato’s “eyes in the sky”, providing surveillance for missions and operations.
A post on the Nato Awacs fleet's account on X late on Thursday said “we raised the security level” but did not elaborate on the nature of the potential threat.
“Operations continue as planned,” it added.
The threat level has been raised to Charlie, which is defined as “an incident has occurred or intelligence has been received indicating that some form of terrorist action against Nato organisations or personnel is highly likely”.
Police confirmed a deployment on Thursday night but gave no details, and offered no information on Friday morning.
Last week, a major German air force base near Cologne was locked down for several hours amid fears that its water supply might have been tampered with.
An investigation found no evidence of such sabotage. There were also reports of suspicious observations at Geilenkirchen and a person was briefly detained for questioning near the base, news agency dpa reported at the time, but there turned out to be nothing untoward.
A spokeswoman for Geilenkirchen on Friday said the current incident was not connected.
Nato through the years – in pictures
Yet it comes at a time of jitters about the potential vulnerability of infrastructure to attempted Russian sabotage.
On Thursday, prosecutors in Flensburg, in Germany's far north, said they were investigating suspicions of espionage for the purpose of sabotage, without elaborating on who might be behind it.
German media reported that drones had been spotted over a chemical park in Brunsbuettel, near the North Sea coast.
Germany, a key ally of Kyiv, has been on high alert for sabotage and attacks on military facilities since Moscow began its invasion of Ukraine in 2022.
In April, investigators arrested two German-Russian men on suspicion of spying for Russia and planning attacks in Germany – including on US army facilities – to undermine military support for Ukraine.
In June, Nato secretary general Jens Stoltenberg said the western military alliance saw a pattern evolving and that recent attacks were a result of Russian intelligence becoming more active.
Several incidents on Nato territory have been treated as suspicious by analysts in recent years, among them the severing of a vital undersea cable connecting Svalbard to mainland Norway in 2022.
