Trump issued a restrained call for peace well after the melee was underway on Wednesday but did not urge supporters to disperse. Earlier he had egged them on to march to Capitol Hill.

The ordinarily mundane procedure of Congress certifying a new president was always going to be extraordinary, with Republican supporters of Trump vowing to protest results of an election that they have baselessly insisted was reversed by fraud.

But even the unusual deliberations, which included the Republican vice president and Senate majority leader defying Trump's demands, were quickly overtaken.

In a raucous, out-of-control scene, protesters fought past police and breached the building, shouting and waving Trump and American flags as they marched through the halls. One person was reported shot at the Capitol, according to a person familiar with the situation. That person's condition was unknown.

The protesters abruptly interrupted the congressional proceedings in an eerie scene that featured official warnings directing people to duck under their seats for cover and put on gas masks after tear gas was used in the Capitol Rotunda.

With the crowds showing no signs of abating, Trump tweeted, "Please support our Capitol Police and Law Enforcement. They are truly on the side of our Country. Stay peaceful!" Earlier, at his rally, he had urged supporters to march to the Capitol.

Senators were being evacuated. Some House lawmakers tweeted they were sheltering in place in their offices.

Demonstrators fought with Capitol Police and then forced their way into the building, not long after a huge rally near the White House during which Trump egged them on to march to Capitol Hill.

Australian Associated Press