The Capitol building in Washington DC is on lockdown owing to a security threat, two days before Joe Biden is inaugurated as US president.

The Capitol, which is home to the US Congress, was attacked by a pro-Trump mob on 6 January, leaving five dead.

Reporters at the scene say an emergency announcement is playing and a rehearsal for Mr Biden's inauguration has been suspended.

Security is tight, with thousands of National Guard members deployed.

Eyewitnesses reported smoke near the Capitol. The Washington DC fire service said it had responded to a fire nearby which was now extinguished.

An alert circulated to Capitol staff said the complex was on lockdown, with no-one being allowed in or out.

All 50 US states and the District of Columbia (DC) are on alert for possible violent protests, ahead of Mr Biden's inauguration on Wednesday.

The FBI has warned of possible armed marches by pro-Trump supporters across state capitols.