(Adds ACLU lawsuit in paragraphs 14-15)
By Sarah N. Lynch and Andy Sullivan
WASHINGTON, June 4 (Reuters) - U.S. Attorney General William Barr said on Thursday that foreign interests and "extremist agitators" tied to the Antifa movement have tried to exploit nationwide protests over the latest in a long series of killings of black men by white police officers.
Barr's statements came three days after an internal intelligence assessment produced by the Department of Homeland Security and seen by Reuters found that most of the violence at the protests appeared to have been carried out by opportunists, not organized extremists.
While Barr and Republican President Donald Trump have focused blame on Antifa, a loosely organized anti-fascist movement, federal prosecutors in Las Vegas on Wednesday charged three members of the far-right "Boogaloo" movement with planning to cause violence and destruction during protests.
"We have seen evidence that Antifa and other similar extremist groups, as well as actors of a variety of different political persuasions, have been involving in instigating and participating in violent activity," Barr said at a news conference.
Barr also defended his decision to forcefully push peaceful protesters back from the White House on Monday evening, saying rioting had gotten out of control over the weekend.
Clearing the protesters allowed Trump to stage a photo opportunity at a nearby historic church, where a fire set during the earlier mayhem did minor damage.
"We decided that we needed more of a buffer to protect the White House," Barr said.
The attorney general has been criticized for his decision to use force on the protests over the death of George Floyd by calling in a wide range of federal agents to protect the White House and other landmarks after demonstrations in Washington turned violent.
The federal agents called in to protect the White House include riot-control teams from the federal Bureau of Prisons, who have been spotted in uniforms without badges or other identification, unlike other police officers.
Bureau Director Michael Carvajal said those agents typically do not wear identifying material on the job, and acknowledged he "probably should have done a better job of marking them nationally."
In a letter to Trump, House of Representatives Speaker Nancy Pelosi, called the presence of unidentified officers and U.S. military on the streets of Washington "alarming."
The Democrat told reporters that her daughter, Alexandra, had been present when the federal agents acting on Barr's orders cleared Lafayette Park near the White House of protesters.
"She thought she had tear gas in her eyes because she was incapacitated for a while and she called me after," Pelosi said.
The American Civil Liberties Union and other groups filed a lawsuit in Washington on Thursday on behalf of the protesters seeking an order declaring that Trump, Barr and other officials violated their constitutional rights.
"When the nation's top law enforcement officer becomes complicit in the tactics of an autocrat, it chills protected speech for all of us," said Scott Michelman, ACLU legal director in the District of Columbia.
Barr said foreign groups are also using social media disinformation campaigns like those mounted by Russia during the 2016 presidential election to widen divisions in U.S. society.
"Some of the foreign hackers and groups that are associated with foreign governments are focusing in on this particular situation we have here, and trying to exacerbate it in every way they can," he said.
Barr said federal agents have made 51 arrests so far for charges involving violence.
He said 114 law enforcement officers have been injured in protests in Washington and 22 have been hospitalized.
Authorities are investigating seven fires set in violent protests in Washington over the weekend, and one person has been arrested and charged, said Regina Lombardo, acting director of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). (Reporting by Sarah N. Lynch and Andy Sullivan; Editing by Jonathan Oatis and Richard Chang)
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