At least four people have been killed in a mass shooting at the Washington Navy Yard, a naval installation in the US capital, a Navy official has said.
Police entered an office building in search of a gunman, after shots were fired at 08:20 local time (13:20 GMT), the US Navy said.
Local news agencies have said a police officer was among the injured. It remains unclear how many were hurt.
Personnel at the yard were ordered to “shelter in place”, the Navy said.
Capt Ed Buclatin, director of public affairs at the Navy Installations Command at the Navy Yard, said on Twitter that four people were killed and eight injured.
The US Navy said shots were reported to have been fired at the Naval Sea Systems Command headquarters at the yard in south-east Washington DC.
Cmdr Tim Juris was on the fourth floor of the building when he heard shots, he told the BBC.
“It sounded like a tap gun as opposed to a real gun,” he said.
Dozens of emergency vehicles have converged on the site, and helicopters have been flying overhead.
President Barack Obama has been briefed on the matter by top officials and has directed federal agencies to co-ordinate their response efforts.
As many as 3,000 people work at the command, which engineers, purchases, builds and maintains ships and submarines for the Navy.
The Washington Navy Yard is the US Navy’s oldest shore installation, first opened in the early 19th Century, according to the Navy. (BBC)