Gunshots were fired Tuesday morning near the entrance of the Pentagon, resulting in multiple injuries. The facility, the headquarters of the US military, was temporarily placed on lockdown.

The Arlington County Fire Department reported multiple patients, but it wasn't immediately clear if they had been shot and the extent of their injuries were unknown.

A police officer was among those injured, according to two law enforcement officials, who spoke on condition of anonymity because they are not authorised to discuss the investigation publicly.

The incident occurred on a Metro bus platform that is part of the Pentagon Transit Centre, the Pentagon Protection Force Protection Agency tweeted. The facility is just steps from the Pentagon building, which is in Arlington County, Virginia, just across the Potomac River from Washington, DC.

An Associated Press reporter near the building heard multiple gunshots, then a pause, then at least one additional shot.

Another AP journalist heard police yelling shooter .

A Pentagon announcement said the facility was on lockdown due to police activity . The agency responsible for security at the building, the Pentagon Force Protection Agency, tweeted shortly before noon that the scene of the incident was secure. The lockdown was lifted except for the area around the crime scene.

Defence Secretary Lloyd Austin and Gen. Mark Milley, chairman of the Joint Chiefs of Staff, were at the White House meeting with President Joe Biden, at the time of the shooting.