The supporters of Donald Trump who attacked the US Capitol were "provoked" by the president and "fed lies," Senate Republican Majority Leader Mitch McConnell said Tuesday.
Mr McConnell’s remarks are his most severe and public rebuke of the outgoing President Trump.
"The mob was fed lies," the senator from Kentucky said in a speech on the Senate floor. "They were provoked by the president and other powerful people.
"They tried to use fear and violence" to stop the certification by Congress of Democrat Joe Biden's November 3 election victory, Mr McConnell said.
"But we pressed on. We stood together and said an angry mob would not get veto power over the rule of law in our nation, not even for one night," he said.
Thousands of Trump supporters stormed the Capitol on January 6 following a speech by the president outside the White House in which he repeated his unsubstantiated claims of having won the election.
At least five people died in the mayhem.
The Democrat-controlled House of Representatives impeached Mr Trump on January 13 for "inciting insurrection" and he faces a potential trial in the Senate after he leaves office on Wednesday.
The votes of 17 Republican senators would be needed to convict Mr Trump in the Senate, and Mr McConnell has not ruled out voting for conviction.
Democrat Chuck Schumer is expected to take over as Senate Majority Leader on Wednesday but Mr McConnell will remain an influential voice in the Republican Party.
Speaking on the Senate floor, Mr Schumer also lashed out at Mr Trump for his role in whipping up the crowd that staged the violent takeover of the Capitol.
"Rioters, insurrectionists, white supremacists and domestic terrorists tried to prevent the transfer of power," he said. "They were incited by none other than the president of the United States."
Mr Biden would be sworn in as the 46th president of the United States on Wednesday "despite what these evil terrorists tried to do", said Mr Schumer.
"The peaceful passing of the torch will take place tomorrow as it has for generations," he said.
Mr Trump's term as president ends on Wednesday when Mr Biden is sworn in.
Mr Schumer added that if Mr Trump is convicted, the Senate would then vote on barring him from running again for president.