The U.S. Navy ships around the Portsmouth Naval Shipyard Tuesday are all part of routine security response training.

Additional security personnel will be at the shipyard, and noise heard along the Piscataqua River near the yard's shorelines. The purpose of the exercise is to improve the training and readiness of Portsmouth Naval Shipyard’s Naval Security Force.

The Shipyard said in a statement that there is no specific threat prompting the activity.

Contact reporter Dan Alexander at or via Twitter @DanAlexanderNH

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