U.S. President Donald Trump has declared an emergency in Washington and ordered federal assistance in preparation for the January 20 inauguration of President-elect Joe Biden.

According to U.S. media outlet The Hill on Monday, this comes after Washington Mayor Muriel Bowser requested that Trump issue the emergency declaration, after a mob of Trump supporters stormed the Capitol, causing a deadly attack.

In the declaration, the White House said the Department of Homeland Security's Federal Emergency Management Agency(FEMA) is authorized to identify, mobilize and provide necessary equipment and resources to alleviate the impact of the emergency.

The protective measures, limited to direct Federal assistance, will be financed by the Federal government.

The Department of Homeland Security is expected to dispatch troops and block public access to the White House and the Capitol starting Wednesday, to prevent a recurrence of such riots.

Earlier on Monday, House Democrats formally introduced an article of impeachment charging Trump with inciting last week's Capitol riot, which led to at least five deaths. The House is expected to vote on the article of impeachment on Wednesday.