One person is dead in a shooting outside the headquarters of the US National Security Agency, according to local media.

Another is reported to have been injured and is in critical condition, reports say.

Local law enforcement officers have told the media that two men tried to ram the security gate of the domestic spying agency's campus in Fort Meade, Maryland.

A report from NBC News says the two men were disguised as women and were driving a stolen car. A senior US official said the incident was not related to terrorism.

Security working at the gate shot one dead and critically injured the other, according to local reports.

Aerial footage released by news networks shows two damaged vehicles parked at an intersection.

Live footage from news helicopters shows uniformed officials closing roads with police tape.

The site of the initial incident appears under control with large numbers of officials present, standing in groups.