The U.S. Capitol is on lockdown with no entry or exit due to an external security threat, local media reported on Monday.

A notice was distributed to Capitol staff saying the complex was on lockdown, with no individual being allowed in or out.

Reports indicate that people who were attending a rehearsal for the Inauguration Day ceremonies were evacuated from the area.

Earlier on, smoke was also seen rising near the governmental building with the city's fire department responding to the incident.

"#DCsBravest responded to an outside fire in the 100 block of H St SE that has been extinguished. There were no injuries. This accounts for smoke that many have seen," the DC Fire and EMS tweeted.

The news comes as defence authorities in the country expressed concerns over an insider attack or other threat from service members involved in securing the inauguration of President-elect Joe Biden.

These worries forced the Federal Bureau of Investigations to vet all of the 25,000 National Guard troops who have been deployed to Washington for the event.

The scare also comes days after the Capitol building was attacked by pro-Trump supporters leaving five people dead.

(With input from agencies)