Donald Trump has pledged there will be an orderly transition after the US Congress formally validated Joe Biden’s presidential election victory on a day that saw a time-honoured ceremony become a nightmare of unprecedented political terror.

The House and Senate certified the Democrat’s electoral college win early on Thursday after a violent throng of pro-Trump rioters spent hours on Wednesday running rampant through the Capitol.

A woman was fatally shot, windows were smashed and the mob forced shaken legislators and aides to flee the building, shielded by Capitol police.

Mr Trump said in a statement tweeted by his social media director Dan Scavino: “Even though I totally disagree with the outcome of the election, and the facts bear me out, nevertheless there will be an orderly transition on January 20th.

“I have always said we would continue our fight to ensure that only legal votes were counted. While this represents the end of the greatest first term in presidential history, it’s only the beginning of our fight to Make America Great Again.”

The rampage began shortly after Mr Trump repeated his unfounded claims of election fraud to thousands of rallying demonstrators he had invited to Washington. Many then surged to the Capitol after he incited them to go there as legislators debated the electoral votes.

More than six hours after the violence erupted, members resumed the session.

Thirteen Republican senators and dozens of party representatives had planned to force debate and votes on the ballots in up to six states.

The assault on the Capitol made some Republicans squeamish about trying to overturn Mr Biden’s win, and challenges were lodged only against Arizona and Pennsylvania. Both efforts lost overwhelmingly.

Mr Biden defeated Mr Trump by 306-232 electoral votes and will be inaugurated on January 20.