US officials have announced fraud charges against the Southern Poverty Law Center (SPLC), a civil rights group that tracks extremist organisations and played a prominent role in confronting the Ku Klux Klan (KKK).

In a news conference on Tuesday, Acting Attorney General Todd Blanche accused the non-profit of secretly funding the very groups that it says it opposes, through paying informants who infiltrated them - including within the KKK.

An indictment charges the SPLC with six counts of wire fraud, four counts of bank fraud and one count of conspiracy to commit money laundering.

The organisation's president has said they would "vigorously defend ourselves, our staff, and our work".

The SPLC has long had a sour relationship with the Trump administration. In October, the FBI ended its relationship with the group after accusing it of being a "partisan smear machine".

Some Republicans have also accused the group of unfairly targeting conservative groups such as Turning Point USA, the Family Research Council and Moms for Liberty, as well as individuals aligned with the Trump administration.

SPLC interim leader Bryan Fair said in video statement before the details of the case were announced that the Alabama-based non-profit organisation has dedicated the last 55 years to "fighting white supremacy and various forms of injustice".

"We are therefore unsurprised to be the latest organisation targeted by this administration," he continued.

He noted that the use of informants by the organisation "was necessary because we are no stranger to threats of violence". He went on to describe a 1983 firebomb attack on the group's office, and repeated threats that SPLC members face.

Tuesday's indictment from the Department of Justice (DOJ) alleges the group paid hundreds of thousands of dollars - and in one case $1m (£740,000) - to informants who were associated or had infiltrated groups that included the neo-Nazi organisation the National Alliance, the KKK and the National Socialist Movement.

It states that the SPLC sent more than $270,000 to a person who helped to plan, and attended, the deadly white nationalist Unite the Right event in Charlottesville, Virginia, in 2017. It does not specify why that person was paid or what type of work they did for the organisation.

In another example, the indictment says the non-profit sent more than $1m over nine years to a person who had infiltrated the National Alliance and stole 25 boxes of documents from the headquarters of the violent extremist group for the SPLC.

It alleges that in total from 2014 to 2023, the SPLC funnelled more than $3m to individuals associated with various violent extremist groups.

The indictment alleges the organisation had been duping its supporters by obtaining "money via donations through materially false representations and omissions about what the donated funds would be used for".

In a news conference, Blanche said: "The SPLC is a non-profit entity that purports to fight white supremacy and racial hatred by reporting on extremist groups and conducting research to inform law enforcement groups with the goal of dismantling these groups."

"The SPLC was not dismantling these groups. It was instead manufacturing the extremism it purports to oppose by paying sources to stoke racial hatred."

Fair, in his video statement, accused prosecutors of "weaponising" the justice system.

"Today, the federal government has been weaponised to dismantle the rights of our nation's most vulnerable people, and any organization like ours that stands in the breach," Fair said.

He also noted that the SPLC no longer worked with paid informants, and that in the past it "frequently" shared information gathered by them with police and the FBI.

"These individuals risked their lives to infiltrate and inform on the activities of our nation's most radical and violent extremist groups," he said.