BERLIN — A major NATO air base in Germany is maintaining a high security alert on Friday, according to a military spokesman.

“At the moment we are still at alert state Charlie,” Donny Demmers, a spokesman for NATO Airbase Geilenkirchen said, noting that the security situation is being closely monitored.

Security alert “Charlie” is implemented at NATO bases when there is an incident or intelligence suggests a likely terrorist action or targeting of personnel or facilities.

The airbase heightened its security level on Thursday based on intelligence indicating a potential threat.

“All non-mission essential personnel have been sent home as a precautionary measure. The safety of our staff is a top priority. Our critical operations will continue as planned,” Demmers said.

The Geilenkirchen base, near the western city of Aachen, houses NATO’s AWACS surveillance aircraft, which provide air and sea surveillance and serve as a flying command center in combat operations.

In recent years, NATO AWACS aircraft have conducted hundreds of flights over Eastern Europe to monitor Russian military activity near the alliance’s borders. — Agencies