The protesters were among about 1,000 demonstrators who marched to the Mobile User Objective System site, the Italian news agency ANSA reported Friday.
Nine protesters climbed antennas inside the base.
Demonstrators claimed the facility would threaten world peace, the environment and the health of locals.
The Italian defense ministry said the base was "essential for NATO operations in the Mediterranean and therefore for national security."
At least one police officer was reportedly injured.
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