The Department of Homeland Security warned on Wednesday of a heightened risk of attacks by “ideologically-motivated violent extremists” on US soil in the wake of Joe Biden’s inauguration, raising the alarm just weeks after the deadly storming of the US Capitol.

DHS said extremists with “perceived grievances fuelled by false narratives”, and who held “objections to the exercise of governmental authority and the presidential transition” could continue to incite or commit violence in coming weeks.

Hundreds of supporters of Donald Trump overwhelmed law enforcement officers to storm the Capitol building this month in protest of the presidential election results, leading to the deaths of five people and interrupting the certification of Mr Biden’s victory.

Warnings advisories on terrorist threats posted by the DHS are more commonly issued about foreign terrorist groups, rather than domestic extremists, and Wednesday’s bulletin underscores persistent concerns about future attacks even after Mr Trump has left office. Since becoming US president a week ago, Mr Biden has ordered officials in his administration to review the threat from violent extremism.

The FBI and Department of Justice have continued to arrest and charge people for unlawfully entering the Capitol earlier this month. In some cases, defendants were charged with carrying illegal firearms, homemade Molotov cocktails and assaulting police officers.

On Wednesday, federal prosecutors said they had indicted three people associated with the Oath Keepers, a paramilitary organisation, for conspiring to obstruct Congress during the storming of the Capitol. Two of the people were also members of Ohio State Regular Militia.

The Capitol breach triggered a massive increase in security ahead of Mr Biden’s inauguration, including the deployment of about 20,000 armed National Guard members in Washington.

Tim Ryan, the Democratic congressman who chairs the House of Representatives committee that oversees the Capitol Police’s $516m annual budget, said on Tuesday that the National Guard would continue to protect the Capitol for a temporary period while a congressional investigation into the security breach took place.

At least two Capitol Police officers have been suspended from duty since the riots, one for allegedly posing for photos with rioters and a second for donning a “Make America Great Again” hat while apparently giving directions to members of the mob.

DHS noted on Wednesday that extremists frequently targeted people with opposing views who were peacefully protesting. Longstanding racial and ethnic tension, including opposition to immigration, were also cited as motivating factors behind some acts of violence.

Threats against critical infrastructure including the healthcare and telecommunications sectors “increased in 2020”, the law enforcement body said, with violent extremists “often citing misinformation and conspiracy theories about Covid-19 for their actions”.