Law enforcement was on high alert around the US Capitol on Thursday after intelligence uncovered a “possible” plot by a militia group to storm the building.

The threat comes two months after a mob of Donald Trump supporters smashed through windows and doors to try to stop Congress from certifying now-president Joe Biden’s victory.

It appears to be connected to a far-right conspiracy theory, mainly promoted by supporters of QAnon, that the former president will rise again to power on March 4 and that thousands will come to Washington DC to try to remove Democrats from office.

March 4 was the original presidential inauguration day until 1933, when it was moved to January 20.

Online chatter identified by authorities included discussions among members of the Three Percenters, an anti-government militia group, concerning possible plots against the Capitol on Thursday, according to two unnamed law enforcement officials.

Members of the Three Percenters were among the extremists who stormed the Capitol on January 6.

The threat came as the Capitol police and other law enforcement agencies were taking heat from Congress in contentious hearings this week about their poor handling of the January 6 riot.

Police were ill-prepared for the mass of Trump supporters in tactical gear, some armed, and it took hours for National Guard reinforcements to come.

By then, rioters had broken and smashed their way into the building and roamed the halls for hours, stalling Congress’s certification effort temporarily and sending politicians into hiding.

“The United States Capitol Police Department is aware of and prepared for any potential threats towards members of Congress or towards the Capitol complex,” Capitol Police said in a statement.

Politicians, congressional staffers and law enforcement officials are still on edge after the January 6 attack, even as security around the Capitol remains at an unprecedented level.

About 5,200 National Guard members remain in DC, the remainder of the roughly 26,000 that were brought in for President Biden’s inauguration that went off with no problems.

There is also a large fence around the US Capitol perimeter that walls off all avenues of entry including on the streets around the building, put in place after the riot.

A former chairman of the House Homeland Security Committee who was among those briefed about a possible new threat against the Capitol said politicians were braced for it.

Republican Representative Michael McCaul said he thought “we’ll see some violence”.

Mr McCaul warned there could be another diversionary tactic — much like the pipe bombs discovered at the political campaign offices on January 6 appeared to be an attempt to lure law enforcement away from the Capitol ahead of the insurrection.