WASHINGTON (Reuters/AFP) - Several people were killed and others injured when at least one gunman opened fire at the United States Navy Yard in Washington on Monday, the authorities said.

A Washington police spokesman said five people had been shot at the Naval Sea Systems Command headquarters, including a District of Columbia police officer and one other law enforcement officer. The Navy did not elaborate.

NBC News, citing a senior naval officer at the Navy Yard, said at least 12 people had been shot, with four killed and eight wounded. This could not be independently confirmed.

A Navy official told Reuters a suspected shooter had been contained, adding that several people died and several others were injured. The total number of victims was unclear, he said on condition of anonymity.

Another Navy official, speaking on condition of anonymity, said more than one shooter may have been involved. The Washington Post reported that there were several shooters.

The Navy said in a statement the shooting took place at the heavily guarded headquarters.

Dozens of police and emergency vehicles surrounded the complex in south-east Washington, which is about 1.6km south of the US Capitol, the local media reported.

Helicopters circled the headquarters, with some touching down on the building's roof, according to a live feed by Washington's WJLA TV.

A Washington police spokesman said the first reports of shots were received at 8.36am.

A White House official said President Barack Obama had been briefed on the shooting. Departures at the US capital's Reagan National Airport were halted for an hour and a half.

The Federal Aviation Administration lifted a ground stop in mid-morning that had been imposed due to the nearby incident, airport spokesman Chris Paolino said.

"Flights have begun to depart, but we expect residual delays as the airport returns to normal operations," Mr Paolino told AFP via e-mail message.

"The ground stop was in place for approximately 90 min," he added.

Earlier, Mr Paolino said departures had been halted due to the shooting but that inbound aircraft were still landing and that the airport remained open.

The Navy Yard dates to the 18th century and is the oldest Navy installation. It houses a museum, the residence of the chief of naval operations and is responsible for weapons development, among other functions.

About 3,000 people work at the headquarters, which is responsible for building and buying US warships and combat systems, the Navy said.

The complex also has a residence that serves as the home of the chief of the US Navy.