Shooters kill 4, wound 8 at Washington Navy Yard

Two suspected shooters, including one in fatigues, were reported "down" after killing at least four people and wounding eight others in a Monday morning rampage at a US naval base in the capital.

As authorities tried to contain the incident at Washington Navy Yard in southeast Washington, police said two shooters "are down" but it was not immediately clear whether the suspected gunmen had been taken into custody or killed.

"Multiple" people have been killed in the shooting at the Washington Navy Yard, Ed Zeigler, director of Public Affairs for Naval District Washington was quoted as saying by CNN.

Air traffic to Reagan National Airport, the closest airport to downtown Washington, was suspended briefly after the incident at 8:20 a.m. when several shots were fired inside the headquarters for Naval Sea Systems Command, the largest of the Navy's five system commands.

Helicopters hovered overhead over the workplace for about 3,000 people, as police with riot and SWAT team gear swarmed the scene. In one chopper, there appeared to be a police sniper peering out, with a scope at the ready, CNN said.

The injured included a Washington police officer who has been hospitalized, and a base security guard officer, according to a Metropolitan Police Department spokesperson.

A White House statement said President Barack Obama was briefed on the situation.