Commenting on the incident a MOD spokesman said:
Two Royal Navy personnel have been involved in a firearms incident at Southampton docks where HMS Astute is alongside. Sadly, one has now died as a result of his injuries.
A third Royal Navy serviceman has been arrested by Hampshire Constabulary and is now in custody. This incident was not terrorist-related and there is no threat to the wider public.
We are co-operating fully with the police investigation and a Royal Navy Service investigation will begin in due course. All concerned family members should call the Joint Casualty and Compassionate Centre on 08457 800 900.
Defence Secretary Dr Liam Fox said:
I am greatly saddened to hear of this incident and of the death of a Royal Navy Service person in this tragic incident. It is right and proper that a full police investigation is carried out and allowed to take its course. My thoughts and sympathies are with those who have been affected and their families.
Those concerned that family members or loved ones may have been involved can call the Joint Casualty and Compassionate Centre incident line on 08457 800 900.