The National Association for the Advancement of Colored People (NAACP) and Rep. Bennie Thompson, the Democratic chairman of the House Homeland Security Committee, on Tuesday filed a federal lawsuit against former U.S. President Donald Trump, his personal attorney, Rudy Giuliani, and two right-wing groups for conspiring to incite the deadly January 6 riot at the U.S. Capitol.

Citing the 1871 Ku Klux Klan Act, the lawsuit, which is expected to be joined by other Democratic lawmakers, accuses the defendants of conspiring to prevent Congress from confirming the election of Joe Biden as president.

Some members of the right-wing groups, Proud Boys and Oath Keepers, have been arrested in connection with that attack.

The suit comes three days after Trump was acquitted of inciting the January 6 riots at his second impeachment trial by the Senate.

"The insurrection was the result of a carefully orchestrated plan by Trump, Giuliani and extremist groups like the Oath Keepers and Proud Boys, all of whom shared a common goal of employing intimidation, harassment and threats to stop the certification of the Electoral College," said a statement by the NAACP.

On his part, Thompson said in a statement: "January 6th was one of the most shameful days in our country’s history, and it was instigated by the President himself. His gleeful support of violent white supremacists led to a breach of the Capitol that put my life, and that of my colleagues, in grave danger."

CNBC quotes Jason Miller, a spokesman for Trump, to have denied the allegations that Trump orchestrated the riots.

"President Trump has been acquitted in the Democrats' latest Impeachment Witch Hunt, and the facts are irrefutable," he said.

"President Trump did not plan, produce or organize the Jan. 6 rally on the Ellipse. President Trump did not incite or conspire to incite any violence at the Capitol on Jan. 6."

(With input from agencies)