A gunman has reportedly barricaded himself inside a room after shots were fired inside a building at the Washington Navy Yard.
According to the Washington Post a police officer was shot nearby.
The US Navy says there are reports of multiple fatalities and injuries in the attack, inside its Naval Sea Systems Command headquarters.
"An active shooter was reported inside the ... building on the Washington Navy Yard at 8:20 am Eastern Time," the Navy said in a statement.
"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."
Around 3,000 people work in the building.
Police from multiple local and federal agencies along with SWAT crews are attending the emergency.
Fox News reporter Peter Doocy said: "It is frantic right now … people are running full steam … all over the place.
"I am looking at what appears to be an all-black armoured vehicle.
"(There are) sirens, ambulances, police cars. Men in full fatigues, with long guns, running down the street.
"Everybody you can think of is here."
A photograph 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.
Link to further information & Videos:
http://news.sky.com/story/1142428/shots ... washington
