All 50 US states and the District of Columbia (DC) are on alert for possible violent protests this weekend, ahead of President-elect Joe Biden’s inauguration on Wednesday.
National Guard troops from across the country are being sent to Washington DC, to discourage any repeat of the deadly riot that unfolded on 6 January.
The FBI has warned of possible armed marches by pro-Trump demonstrators at all 50 state capitols.
The National Mall in DC has been shut.
Barricades are lining the streets of the capital amid tightened security.
Police confirmed on Saturday that a Virginia man had been arrested a day earlier with two handguns and 509 rounds of unregistered ammunition, as he tried to pass through a Capitol Police checkpoint.
He was carrying a “non-government issued credential”, police said.
Responding on Twitter, Representative Don Beyer of Virginia said “the danger is real”, and urged people to avoid the Capitol area.