Two gunmen have shot 12 people, killing four, in an attack at the US Naval Sea Systems Command headquarters in Washington, according to police sources.
The men, one dressed in military fatigues, launched their attack on one of the biggest naval command buildings in the US in the early morning rush as people arrived for work. Navy officials have said that they were dealing with two gunmen and later confirmed that one had been killed.
Washington Post were reporting the men had shot dead four people and injured eight, sparking fears that it could be a terrorist attack. Six schools in Washington have been put on lockdown.
Authorities have officially confirmed only that there have been several fatalities and that at least 10 have been injured.
The US President Barack Obama is being regularly briefed on the rapidly unfolding situation as law enforcement teams attempt to locate the gunmen inside the naval base.
Police and federal agents from multiple law enforcement agencies responded as the base, where 3,000 people work, was secured while officers searched for the shooter inside the complex.
Ambulances were parked outside, streets in the area were closed and flights at Reagan National Airport were temporarily halted.
Witnesses described a gunman opening fire from the fourth floor, aiming down on people in the first-floor cafeteria. Others said a gunman fired at them in a third-floor hallway.
Patricia Ward, who works at the command centre, and witnessed the attack said "It just happened so fast." She said that a gunman had been shooting into the atrium and added "but I didn’t pay any attention to that, I just kept on running."
Responding to questions about the level of security at the base Ms. Ward said "It's not secure enough for me." She said that staff had to have a card to get on to the complex and that without one it would be difficult to pass security.
One of the gunmen, has been described as black, wearing dark clothing and around 5ft 10ins. They were said to have been carrying AR-15 rifles.
The weapon is the country's best selling rifle and the same weapon used in the both the Aurora cinema shooting where 12 were killed and the Sandy Hook school shooting in Connecticut last year, where gunman Adam Lanza killed 20 children.
A Navy statement said "An active shooter was reported inside the ... building on the Washington Navy Yard at 8:20 am Eastern Time. Emergency personnel remain on scene and a 'shelter in place' order has been issued for Navy Yard personnel. This release will be updated as new information is confirmed."
A photograph said to have been taken in the yard shows one man lying on the ground and being treated by members of the public.
Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. It builds, buys and maintains the Navy's ships and submarines and their combat systems.
Dr. Janis Orlowski is spokesperson at Washington Hospital Centre. She says they are expecting more of the injured to arrive at the facility.
