The US Capitol building is on lockdown

We will use your email address only for sending you newsletters. Please see our Privacy Notice for details of your data protection rights.

Sign up fornow and never miss the top politics stories again.

Members were locked in the chamber and emergency protocols initiated as armed cops descended on the heart of American power in Washington.

Fox News reported that the lockdown was initiatiated by the arrest of a gunman near the US Department of Labour, which is close to the Senate chamber side of the Capitol complex.

The channel added that two people had been arrested by police and that members continued to vote during the drama.

There were initially reports of a shooting incident, but police later said there were no shots fired and nobody was injured.

However, Capitol Police issued instructions to aides to take immediate shelter and to keep away from windows amid heightened security.

It is the second time in five days that the Senate building has been placed on lockdown due to security threats. On Friday a gun scare in one of the Capitol's tunnels forced a huge security operation.

A Senate Police spokesman said: "Due to a security threat, no entry or exit is permitted at this time in any building of the Capitol Complex."

It is understood that the incident is not specifially related to a threat to the Capitol or US politicians, and that counter-terrorism police and the FBI are not involved in the investigation.

According to reports, police were pursuing a number of suspects near to the complex when the security scare broke out, forcing security to hit the red alert button.

The lockdown has since been lifted.