The Pentagon, which houses the headquarters of the United States Department of Defense, was briefly put under a lockdown on Tuesday due to "shooting incident" at a nearby Metro station.

The lockdown was later lifted and the building reopened a short while later, the Pentagon Force Protection Agency said.

"The Pentagon has lifted the lockdown and has reopened. Corridor 2 and the Metro entrance remains closed. Corridor 3 is open for pedestrian traffic," the PFPA informed through a tweet.

The shooting incident took place outside the building on the Metro Bus platform, which is a major entrance to the Pentagon used by thousands of personnel every day entering and leaving the building.

"The Pentagon currently is on lockdown due to an incident at the Pentagon Transit Center. We are asking the public to please avoid the area. More information will be forthcoming," PFPA said after the incident.

Meanwhile, the PFPA has advised people to stay away from the Metro rail entrance and bus platform area as it was still an active crime scene.

"The scene of the incident is secure. It is still an active crime scene. We request that everyone stay away from the Metro rail entrance and bus platform area. Transportation at the Pentagon is diverted to Pentagon City," tweeted the Agency.