A lockdown on the US Capitol building has been lifted after shots were fired in the visitors centre, police say, with the gunman injured and taken into custody.

Key points: Gunman in custody after being shot at US Capitol Visitors Centre

Gunman in custody after being shot at US Capitol Visitors Centre Female bystander also injured

Female bystander also injured Incident forced temporary lockdown of White House

During a routine security screening, a man drew what appeared to be a gun and pointed it at officers, US Capitol police chief Matthew Verderosa said outside the building, the seat of the United States Congress.

"An officer fired and struck the suspect, who was subsequently treated by medical personnel," he said. "A weapon was recovered on the scene."

While the male suspect's identity was not confirmed, authorities said he was known to local police.

The suspect is currently in surgery but his condition is unknown.

Police said a female bystander also suffered what appeared to be minor injuries and was transported to the hospital.

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Earlier reports that a police officer was wounded in the incident were false, police chief Verderosa said.

He said an initial investigation indicated "this is an act of a single person who has frequented the Capitol grounds before and there is no reason to believe that this is anything more than a criminal act".

There was confusion in early accounts about what occurred, after gunshots were heard at the visitors centre, where workers were told to take shelter.

"There has been an isolated incident at the US Capitol. There is no active threat to the public," Washington DC police said on Twitter.

The US Secret Service, meanwhile, said earlier reports that the gunman tried to gain entry to the White House were incorrect.

Sorry, this video has expired White House in lockdown after shots fired

Tourists at visitors centre told to 'stay low'

The visitors centre — where tourists go through security and begin their guided tours of the domed building — remained closed to the public afterwards.

Jeff Westbrock, a North Carolina resident who was visiting Washington with his family, was in the main lobby of the centre when the shots were fired.

"We covered each other up, Capitol police told everybody to stay low, and they neutralised the situation and told us to go into the auditorium and to stay safe," he told the news agency AFP.

Sophie Kneschke, a tourist from Germany, said it had been a scare.

"We were just about to leave when I just saw a security man running in the hall and I didn't think of anything bad until people told us to lie on the ground and don't move and everything," she said.

"I was pretty much in panic because I didn't know what was going on.

"We went with some employees of the building to an emergency exit and we stayed there until security men came and then we got evacuated."



White House lockdown

The White House, where thousands were attending the annual Easter Egg Roll, was briefly on lockdown, but the order was quickly lifted.

The shooting happened just a few hours after a drill for an active shooter took place at the Capitol, creating further confusion.

Cathryn Leff, a licensed therapist, tweeted that she was at the visitor's centre when she heard gunshots while going through a security checkpoint.

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The Secret Service temporarily cleared tourists from an area surrounding the White House after the incident, but activities quickly went back to normal.

The north and south fence lines around the White House complex were closed as a "routine precautionary measure", a spokesman from the Secret Service said.

A US Secret Service agent stands guard at the White House. ( AFP: Nicholas Kamm )

AFP/Reuters