WASHINGTON:A Democratic congressman, in a lawsuit filed on Tuesday, accused former President Donald Trump, his personal lawyer Rudy Giuliani and two right-wing groups of conspiring to incite last month's deadly riot at the U.S. Capitol.

The civil lawsuit accuses them of violating the Ku Klux Klan Act, an 1871 law passed to crack down on the white supremacist organization. It is the latest legal attempt to find Trump responsible for the violence on Jan. 6, after he spent months falsely claiming his election defeat in November was the result of widespread fraud.

It also names as defendants the Proud Boys, a far-right organization, and the anti-government militia known as the "Oath Keepers."

"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," according to a press release announcing the lawsuit.

The U.S. Senate on Saturday acquitted Trump of inciting the Jan. 6 riot, when 57 senators, including seven Republicans, voted to convict, short of the 67 votes needed.

Representative Bennie Thompson, a Democrat who chairs the House of Representatives Homeland Security Committee, is the named plaintiff on the suit filed in U.S. District Court in Washington.

It seeks compensatory and punitive damages without citing a dollar figure, as well as an award for attorneys fees. In addition, it asks a federal judge to issue an order barring Trump and his co-defendants from future violations of the law.

Thompson says he heard threats and a gunshot during the attack on the Capitol and had to hide from the mob.

The National Association for the Advancement of Colored People and attorneys from the law firm Cohen Milstein Sellers & Toll PLLC are handling the litigation.

Giuliani did not respond to a request comment.

Jason Miller, an adviser to Trump, said Giuliani "is not currently representing President Trump in any legal matters" and he dismissed the allegations in the lawsuit, citing Trump's acquittal in the Senate.

"President Trump did not plan, produce or organize the Jan. 6th rally on the Ellipse," Miller said in a statement, referring to a speech the Republican former president made that day at a rally near the White House.

Indiana University law professor Gerard Magliocca said Trump will likely be dismissed as a defendant from the lawsuit because of a U.S. Supreme Court decision from 1982 that protects presidents from lawsuits over official acts.

"I don't see how the tort suit can proceed" against Trump, Magliocca said, adding that in his view, Trump's speech was within the scope of his official duties.

Critics have said that Trump and Giuliani helped incite the rioters during the Jan. 6 "Save America" rally, where both repeated false claims that the election had been stolen.

Giuliani told the crowd "let's have trial by combat... I'll be darned if they're going to take our free and fair vote."

Trump, who then took the stage, urged people to march to the Capitol. More than 200 people have been charged with federal offences in the assault on Congress, which left five dead.

The lawsuit also discusses actions Trump took prior to the riots, as evidence he helped to incite them.

After officials in states such as Georgia, Arizona and Michigan warned of possible threats of violence, for instance, the lawsuit alleges that Trump "endorsed rather than discouraged" those threats.

The FBI and federal prosecutors have been increasingly focusing on whether members of far-right extremist groups conspired to impede Congress from certifying President Joe Biden's election victory.

At least 18 people associated with the Proud Boys have been charged so far for their alleged role during the riots. Several of the alleged Proud Boy associates have been accused of conspiring to impede Congress or block police from protecting the Capitol.

Three alleged associates of the Oath Keepers have also been indicted on charges they conspired to storm the U.S. Capitol as far back as November. One of them - Thomas Caldwell - pleaded not guilty last week.

Reuters has reported that the Justice Department is also considering whether to charge members of the groups under the federal Racketeer Influenced and Corrupt Organizations Act, known as RICO, normally used against organized crime. A decision on that has not been made.

Other members of Congress, including Democratic Representatives Hank Johnson and Bonnie Watson Coleman, are expected to join the lawsuit.