A Royal Navy serviceman was arrested today over a shooting on board a nuclear-powered submarine which left one of his colleagues dead and a second with life-threatening injuries.
Local civic dignitaries, including the mayor and council leader were visiting HMS Astute, which is currently docked in Southampton, at the time of the incident.
The Ministry of Defence said the shooting was not terrorist-related and there was no threat to the wider public.
An 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. The Royal Navy is now attempting to inform their families as a matter of urgency.
"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."
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."
Southampton City Council's leader Royston Smith, mayor Carol Cunio, and chief executive Alistair Neill were on board HMS Astute at the time of the shooting.
A spokesman for the local authority said: "We can confirm they are safe and unharmed and should be coming off and taken away by car soon. They have clearly been through a traumatic experience."
Police were alerted to the shooting by the Ministry of Defence at 12.12pm today.
"We believe two people have sustained injuries as a result of gunshots which have been discharged aboard the vessel," Hampshire Police said in a statement.
Armed police, firefighters, paramedics and the Hampshire and Isle of Wight Air Ambulance helicopter were sent to the dockside where the submarine was berthed.
The MoD said people concerned about loved ones on the vessel should contact its Joint Casualty and Compassionate Centre incident line on 08457 800900.
HMS Astute, the Navy's newest and most advanced submarine, is docked at Southampton's Eastern Docks on a five-day official visit to the city.
It was scheduled to host visits from Sea Scouts and local school and college pupils from Southampton and the New Forest.
HMS Astute previously hit the headlines when it ran aground on a shingle bank between the Scottish mainland and the Isle of Skye and remained marooned for several hours.
The embarrassing incident in October last year cost Commander Andy Coles his command of the submarine. He was replaced by Commander Iain Breckenridge.
HMS Astute was named and launched by the Duchess of Cornwall in June 2007 before being welcomed into the Royal Navy in August last year at a commissioning ceremony at Faslane Naval Base on the Clyde.
The submarine weighs 7,800 tonnes, equivalent to nearly 1,000 double-decker buses, and is almost 328ft (100m) long.
Its Spearfish torpedoes and Tomahawk cruise missiles are capable of delivering pinpoint strikes from 1,240 miles (2,000km) with conventional weapons.
The submarine's nuclear reactor means that it will not need refuelling once in its entire 25-year life and it makes its own air and water, enabling it to circumnavigate the globe without needing to surface.
Built by defence giant BAE Systems at Barrow in Furness, Cumbria, it was the first in a fleet of six which will replace the Trafalgar class submarine.
The grey silhouette of the submarine could be seen berthed up against the dockside.
A nearby P&O cruise-liner awaiting to depart dwarfed the tiny submarine, which was being patrolled by two police launches.
A passer-by, who did not wish to be named, said he saw emergency vehicles "swarming" around the area.
He said: "There were several ambulances, two fire engines, there are two police boats - they were swarming all over the place.
"Quite a while later the air ambulance took off."
Another man said: "It's shocking, that's not what you'd expect to happen, it's not a very good state of affairs."
Jan Brunning, from Lymington, Hampshire, said: "It's a very unlucky sub, one could say cursed.
"We just came down here to get on our boat and there were police everywhere."
Another member of the public, who helped design Astute for BAE Systems, and who also served in the Royal Navy, said: "I decided to come down here because I spent 10 years designing the thing.
"I wasn't a submariner but I was in the Navy so I understand the pressures of serving on a submarine and understand why something like this possibly might happen.
"When I was in the Navy, they would give us a gun but wouldn't give us ammunition to put in it, they didn't trust us."
The seriously injured Navy crew member was taken to Southampton General Hospital, South Central Ambulance Service said.
The medical response to the shooting comprised one land ambulance crew, the air ambulance, an ambulance supervisor, an emergency care practitioner and two doctors.