The Federal Bureau of Investigation (FBI) has warned of the possibility of armed protests being held across the US in the days before Joe Biden is sworn in as president.
There are reports of armed groups planning to gather at all 50 state capitols and in Washington DC in the run-up to his 20 January inauguration.
The fears come as security plans are tightened for the event itself, reports BBC.
On Monday, Mr Biden said he was not afraid to take the oath of office at the ceremony at the Capitol.
Both he and Vice-President-elect Kamala Harris are expected to be sworn in there, only two weeks after it was the site of a deadly raid by radical supporters of President Donald Trump opposing the election result.
Security officials are resolute there will be no repeat of the breach seen on 6 January – when thousands of pro-Trump supporters were able to break into the grounds of the complex where members of Congress were voting to certify the election result.
Chad Wolf, acting head of the Department of Homeland Security (DHS), said on Monday that he had instructed the US Secret Service to begin special operations for the inauguration on Wednesday – six days early – “in light of events of the past week and the evolving security landscape”.
Officials say up to 15,000 National Guard troops could be made available to fortify the event. Later on Monday, Mr Wolf became the third Trump cabinet secretary to step down since the Capitol riots, after Betsy DeVos and Elaine Chao.
Mr Wolf’s exit plunged his department into turmoil just as it gears up to handle security for the Biden inauguration. Mr Wolf last week called on Mr Trump to “strongly condemn” the protesters who stormed Congress.
The outgoing secretary said his departure had been prompted by “recent events”, including court rulings challenging the legal validity of his appointment.
What further protests are planned?
Law enforcement around the country are said to be bracing for the possibility of further violence in the days before Joe Biden takes office.
Posts on pro-Trump and far-right online networks have called for protest action on a number of dates, including armed demonstrations in cities across the country on 17 January and a march in Washington DC on inauguration day itself.
What security is planned for the inauguration?
On Monday President Trump declared a state of emergency until 24 January, which enables the Department of Homeland Security to act to “avert the threat of a catastrophe”.
The DHS announced it is starting a National Special Security Event operations six days earlier than planned, starting from Wednesday. The designation allows security agencies to work together on protective measures such as road closures.
More than 10,000 National Guard troops will be the capital by the weekend, with about 5,000 more available if requested, promised Chief of the National Guard Bureau General Daniel Hokanson.
What is the latest on impeachment efforts?
The warnings about further pro-Trump violence come as efforts move forward to impeach the president for his role in last week’s deadly invasion of the Capitol.
An article filed in the House on Monday accuses Mr Trump of “incitement of insurrection” during a rally in which Mr Trump alleged, without evidence, that November’s presidential election was “stolen” from him.
Democrats say a vote on the article will go ahead in the House on Wednesday unless Vice-President Mike Pence invokes constitutional powers to remove Mr Trump from office.