One person has been killed and another is in a critical condition after a shooting on board a nuclear submarine, police said.

One person has been killed and another is in a critical condition after a shooting on board a nuclear submarine, police said.

One man has been arrested after the incident on HMS Astute, which is docked in Southampton, but Hampshire police are refusing to comment on reports that the three people involved are all service personnel.

They said the incident was not terrorist related and there was no risk to the public.

Several police vehicles were sent to the Eastern Docks and officers could be seen on the gangway of the £1bn submarine.

A police spokesman said: "Hampshire police were called by their Ministry of Defence colleagues at 12.12pm today and are currently liaising with them to establish the exact circumstances of the incident.

"It is believed two people have sustained injuries as a result of gun shots being discharged on the vessel. People should be reassured there is no risk to public safety.

"Hampshire Constabulary and the MoD are keen to stress this incident is not terrorist related. More information will be circulated as it becomes available," the police said.

The MoD referred all calls to Hampshire police.

HMS Astute is described by the Royal Navy as the first of a new class of vessel designed to be the largest and most powerful nuclear attack submarines ever built for it.

Built in Barrow-in-Furness, Cumbria, and based at Faslane, in Scotland, this is Astute's first trip south.

The five-day visit to Southampton was billed as the first chance for people outside north-west England and Scotland to see the boat.

Astute was not open to the public while in Southampton, but civic leaders, sea cadets, scouts, and school and college parties were being invited on to the 7,500-tonne vessel.

Astute's commanding officer, Commander Iain Breckenridge, said before arriving in Southampton: "My ship's company and I are very much looking forward to the visit and meeting the people of the city. And I'm sure scouts, school pupils and other visitors will be impressed with the capabilities of this formidable vessel."

Since commissioning last August, the boat has had what the navy calls an interesting time, including running aground off the Isle of Skye. It is now in the middle of a "demanding" trials programme.

The submarine's Spearfish torpedoes and Tomahawk cruise missiles are capable of delivering pinpoint strikes from 1,240 miles with conventional weapons. Its nuclear reactor means it does not need refuelling and it makes its own air and water, enabling it to circumnavigate the globe without needing to surface.

It was the first in a fleet of six which will replace the Royal Navy's Trafalgar class submarines.