Calls to the US Navy's 6th Fleet, which oversees European operations, were not answered and an email to the fleet was not immediately acknowledged.
Online posts described Naval Air Station Sigonella as being locked down "due to an ongoing situation".
NAS Sigonella hosts US Navy P-8 Poseidon reconnaissance aircraft, as well as MQ-4C Triton drones.
A US air base in Italy has gone into lockdown over an unspecified incident.
There are also US Space Force personnel based there who work on identifying possible missile threats in the region.
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