Canadian Prime Minister Justin Trudeau on Friday accused President Donald Trump of having "incited" his supporters to storm the US Capitol on Wednesday.

"We were all shocked to see extremists incited by the president to act so violently to wreck the Capitol in Washington," Trudeau told a news briefing at his official residence in Ottawa.

"I think we all saw what the president said, we all saw the horrifying scenes of a violent mob who wanted to overthrow democratic institutions in the United States," he said in one of his most vocal criticisms of the outgoing US president, with whom he has had a difficult relationship.

A crowd of pro-Trump demonstrators stormed the Capitol on Wednesday, interrupting lawmakers' certification of Joe Biden's election win by both houses of Congress. The death toll rose to five dead on Friday, after a police officer succumbed to injuries sustained in the clashes.

"I think it's extremely important to remember that we all have a responsibility as citizens, but also as leaders, to choose our words well, to make the right choices to bring people together, to respect the different points of view and never leave room for hatred, for extremism, for violence," he added.

On Monday, Enrique Tarrio, chairman of the far-right US-based Proud Boys group, was arrested over the torching last month of a Black Lives Matter banner taken from a church during violent protests. Several people were stabbed and dozens more arrested in that unrest.

Asked about the possibility of listing the Proud Boys as a terrorist entity, Trudeau was evasive, promising to "continue to fight against violent extremism that we see more and more" around the world.

"Our security agencies take this very seriously," he added.

The scenes of violence on Capitol Hill were condemned by many world leaders, including Trudeau, who on Wednesday expressed the deep concern of Canadians over the "attack on democracy."