Supporters of U.S. President Donald Trump attend a rally to contest the certification of the 2020 U.S. presidential election results by the U.S. Congress, in Washington, U.S, January 6, 2021. REUTERS/Shannon Stapleton

Swarms of protesters stormed the US Capitol on Wednesday as they sought to force Congress to undo President Donald Trump’s election loss, temporarily suspending a last-ditch effort by some of Trump’s fellow Republicans to throw out the results.

Police fired tear gas and ordered several office buildings to be evacuated as protesters breached the Capitol and were seen marching through the halls of Congress, where lawmakers were meeting to certify President-elect Joe Biden’s victory.

Police escorted House of Representatives members from the chamber where they had been debating after lawmakers aligned with Trump challenged the election results — an effort unlikely to succeed. The Senate abruptly adjourned and Vice President Mike Pence, who had presided over a joint session of Congress, was escorted from the chamber.

Capitol Police told lawmakers in the House chamber to take gas masks from beneath their seats and prepare to put them on. Officers at the front door of the House chamber had their guns drawn as someone attempted to enter the chamber.

Officers ordered people in the chamber to drop to the floor for their safety.

The chaotic scenes came after Trump addressed thousands of supporters near the White House, repeating his baseless claims that the election was stolen from him due to widespread fraud. Election officials of both parties and independent observers have said there was no significant fraud in the Nov. 3 contest, which Biden won by more than 7 million votes in the national popular vote.

Weeks have passed since the states completed certifying that Biden, a Democrat, won the election by 306 Electoral College votes to Trump’s 232. Trump’s extraordinary challenges to Biden’s victory have been rejected by courts across the country.

Trump had pressed Pence to throw out election results in states the president narrowly lost, though Pence has no authority to do so.

The certification in Congress, normally a formality, was expected to stretch for several hours as some Republican lawmakers mounted an effort to reject some state tallies, starting with Arizona.

Outside the Capitol, members of militia groups and far-right groups, some in body armor, mingled with the crowds. Protesters chanting pro-Trump slogans overturned barricades and clashed with police.

On Twitter, Trump called on protesters to stay peaceful.

Washington D.C. Mayor Muriel Bowers ordered a citywide curfew starting at 6 p.m.