WASHINGTON (AFP) - The US Navy on Thursday identified the civilian who killed a sailor aboard a destroyer in Virginia this week, saying he stripped a guard of his gun before opening fire.

The incident, at America's largest naval base, has raised fresh questions about security at military installations after a shooting rampage last September at the Washington Navy Yard when a civilian contractor killed 12 people.

Authorities said Jeffery Savage, 35, a truck driver who had driven his vehicle on to the Norfolk naval base on Monday, tried to board the USS Mahan, a guided-missile destroyer, but was told to stop and confronted by security officers.

"A struggle occurred and Savage was able to disarm the petty officer of the watch," according to a statement from the Naval Criminal Investigative Service (NCIS).

Savage used the gun to kill Master-at-Arms 2nd Class Mark Mayo before other security guards shot him dead, it said.

Savage had served time in prison for voluntary manslaughter and selling cocaine, according to The Virginian-Pilot and other local media.

The shooter had a valid transportation worker credential, but officials said that alone does not provide access to a base as it must be used along with other documents.

"The NCIS investigation has confirmed that Savage had no reason or authorisation to be on Naval Station Norfolk," it said.

"The chain of events that allowed Savage entry to the installation and the ship are under investigation."

Defence Secretary Chuck Hagel, in response to the Navy Yard shooting in September, announced new measures this month designed to counter "insider" attacks at military bases and bolster vetting for security permits.

Hagel said the Pentagon would create an automated "continuous" review of security clearances issued to employees and contractors.

The system will screen those with access to classified information in real time against criminal records or other information that might raise alarms about their trustworthiness or mental condition.