FBI warns of armed protests amid fears of more pro-Trump violence

The FBI has warned of armed protests set to be held across the US in the days before Joe Biden is sworn in as president.

Investigators believe some of the people are members of extremist groups, the officials said.

The fears come as security plans are hardened for the event itself.

There are numerous reports of armed groups planning to gather at all 50 state capitols and in Washington DC in the run-up to his inauguration on 20 January.

On Monday, Mr Biden told reporters he was not afraid to take the oath of office outside of the US Capitol.

Both he and Vice-President-elect Kamala Harris are still expected to be sworn in outside the building, despite the deadly raid by radical supporters of President Donald Trump opposing the election result last week Wednesday.

Security officials are taking all precautions to avoid a 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.

The riots followed weeks of online calls for violence in the nation's capital in the final days of Donald Trump's presidency.

A tweet in which Mr Trump promised that last Wednesday's event in Washington "will be wild" fuelled a "month-long frenzy of incitements, strategising, and embrace of violence against lawmakers," according to a research group that tracks online extremism activity.

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".

Late on Monday, Mr Wolf became the third Trump cabinet secretary to step down since the Capitol riots, after Betsy DeVos and Elaine Chao.

The outgoing secretary said his departure had been prompted by "recent events", including court rulings challenging the legal validity of his appointment.

Meanwhile, up to 15,000 National Guard troops could be made available to fortify the event, officials have said.

Army Gen Daniel Hokanson, chief of the National Guard Bureau, told reporters on Monday that the Guard is also looking at any issues across the country.

"We're keeping a look across the entire country to make sure that we're monitoring, and that our Guards in every state are in close coordination with their local law enforcement agencies to provide any support requested," he said.

An internal FBI bulletin, reported by ABC News and other outlets, carries a warning that one group is calling for the "storming" of state, local and federal courthouses around the country if Mr Trump is removed from office early and on inauguration day if he is not.

Calls for Mr Trump's resignation, removal from office or impeachment have grown among Democrats and some Republicans in the days following the riots.

A report also issued, by Site Intelligence Group on Saturday has also warned that the Capitol attack has emboldened Trump-supporting extremists.

The talk of armed marches next week is not limited to "radicalised" Trump supporters.

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.

Donald Trump has said he will not attend the inauguration - becoming the first president in more than 150 years not to do so.