Stewart Rhodes, the founder and leader of the far-right Oath Keepers militia group, has been arrested and charged with seditious conspiracy in the 6 January attack on the US Capitol, the Department of Justice said on Thursday.

Ten others face the same charge, which carries a maximum penalty of 20 years in prison.

Announcing the first seditious conspiracy charges brought in connection with the Capitol attack, the justice department said members of the extremist group came to Washington intent on stopping the certification of Joe Biden’s victory over Donald Trump in the presidential election.

Rhodes, 56 and from Granbury, Texas, is the highest-ranking member of any extremist group to be arrested in relation to the attack.

The justice department said Rhodes and Edward Vallejo, 63, of Phoenix, Arizona, were “being charged for the first time in connection with events leading up to and including 6 January. Rhodes was arrested this morning in Little Elm, Texas, and Vallejo was arrested this morning in Phoenix.”

The nine others already faced charges in connection with the Capitol attack, among more than 725 individuals to do so.

In its statement, the justice department described the Oath Keepers as “a large but loosely organised collection of individuals, some of whom are associated with militias.

“Though the Oath Keepers will accept anyone as members, they explicitly focus on recruiting current and former military, law enforcement and first-responder personnel. Members and affiliates of the Oath Keepers were among the individuals and groups who forcibly entered the Capitol on 6 January 2021.”

Rhodes did not enter the Capitol but is accused of helping put into motion violence that disrupted the certification process.

Thousands of pro-Trump rioters stormed past police barriers and smashed windows, entering the building, injuring dozens of officers and sending lawmakers into hiding. Five people died, including a Capitol police officer and a Trump supporter shot by law enforcement.

Some in the mob erected a gallows outside the Capitol. Some chanted “Hang Mike Pence” as they searched for the vice-president, who was presiding over certification.

Pence rejected pressure from Trump and advisers who said it was within his power to block certification, citing unfounded claims of electoral fraud in battleground states, and throw the election to the US House.

Scenes from the attack on the Capitol were broadcast around the world. The justice department release described one of the most indelible moments.

At approximately 2.30pm, it said, some of the men now charged with seditious conspiracy and other “Oath Keepers and affiliates – many wearing paramilitary clothing and patches with the Oath Keepers name, logo, and insignia – marched in a ‘stack’ formation up the east steps of the Capitol, joined a mob, and made their way into the Capitol.

“Later, another group of Oath Keepers and associates … formed a second ‘stack’ and breached the Capitol grounds, marching from the west side to the east side of the Capitol building and up the east stairs and into the building.

“While certain Oath Keepers members and affiliates breached the Capitol grounds and building, others remained stationed just outside of the city in quick reaction force (QRF) teams. According to the indictment, the QRF teams were prepared to rapidly transport firearms and other weapons into Washington DC in support of operations aimed at using force to stop the lawful transfer of presidential power.

“The indictment alleges that the teams were coordinated, in part, by [Thomas] Caldwell [67 and of Berryville, Virginia] and Vallejo.”

The attempt to stop certification failed. Though more than 700 people have been charged over the riot, no politician has yet been formally punished.

Steve Bannon, an adviser to Trump, has pleaded not guilty to a charge of criminal contempt of Congress, for refusing to cooperate with the House committee investigating the attack. Mark Meadows, Trump’s last White House chief of staff, could face the same charge.

Trump himself was impeached for a second time over the riot but acquitted of inciting the insurrection when enough Republican senators stayed loyal. Senior House Republicans including the minority leader, Kevin McCarthy, have refused to cooperate with the select committee.

Amid reaction to the charges against the Oath Keepers on Thursday, Matthew Miller, a political analyst and former justice department official, wrote: “The seditious conspiracy charges are important for a lot of reasons, but in my mind the most important is that, should they be convicted, the Oath Keepers will be forever branded as traitors to their country.”

Regarding the arrest of Rhodes, the Lincoln Project, a group of Republican anti-Trump operatives, said: “Alternative headline: Key GOP Coalition Leader Arrested in 6 January Investigation.”