Navy officials said the threats Wednesday targeted Naval Station Norfolk and Joint Expeditionary Base Little Creek in nearby Virginia Beach.
The base in Norfolk has resumed normal operations after sweeping areas of the base and finding no threats. But Little Creek in Virginia Beach is continuing to investigate.
The base received four separate threats via telephone. Two involved ships, the USS Whidbey Island and USS Gunston. And two were made to base buildings, the Admiral Joel T. Boone Branch Medical Clinic and the Personnel Support Detachment.
The threats come two days after a sailor on watch in Norfolk reported seeing a trespassing scuba diver near a pier. The sighting proved to be unfounded after a search.