US military personnel were ordered to take cover at RAF Lakenheath following ‘suspected unauthorised drone activity’.
The base, which hosts American military forces in the UK, saw an alert message sent to all workers.
It was headed with the words ‘REAL WORLD’ written in red capital letters.
The alert continued: ‘Seek the nearest shelter-in-place room.’
A US Air Force spokesperson confirmed they responded to ‘suspected unauthorised drone activity’, adding ‘no personnel, aircraft or infrastructure were affected’.
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They said: ‘We continue to work closely with our host nation counterparts to ensure the safety and security of our US service members, US and host nation civilians, contractors, and all of our families.
‘Protecting our shared community is a joint responsibility, and we encourage everyone to support this effort by reporting any unusual or suspicious activity to local authorities.’
The Ministry of Defence said: ‘We are coordinating with all relevant parties regarding reports of unauthorised drone activity at RAF Lakenheath this evening.
‘USAF Security Forces personnel responded to the reports and the situation is now resolved. We are working closely with them to establish the facts. We will provide updates in due course.’
It comes as all US flights were grounded following a communications error.
The glitch caused havoc for thousands of passengers, with 15,000 flights delayed or cancelled.
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