WASHINGTON (NYTIMES) - US Attorney General William Barr told federal prosecutors in a call last week that they should consider charging rioters and others who committed violent crimes at protests in recent months with sedition, according to two people familiar with the call.

The highly unusual suggestion to charge people with insurrection against lawful authority alarmed some on the call, which included US attorneys around the country, said the people, who spoke on the condition they not be named describing Mr Barr's comments because they feared retribution.

The attorney-general has also asked prosecutors in the Justice Department's civil rights division to explore whether they could bring criminal charges against Mayor Jenny Durkan of Seattle for allowing some residents to establish a police-free protest zone near the city's downtown for weeks this summer, according to two people briefed on those discussions.

The directives are in keeping with Mr Barr's approach to prosecute crimes as aggressively as possible in cities where protests have given way to violence.

But in suggesting possible prosecution of Ms Durkan, a Democrat, Mr Barr also took aim at an elected official whom President Donald Trump has repeatedly attacked.

A Justice Department representatives did not respond to requests for comment. The Wall Street Journal first reported Mr Barr's remarks about sedition.

The disclosures came as Mr Barr directly inserted himself into the presidential race in recent days to warn that the United States would be on the brink of destruction if the president was not reelected.

He told a Chicago Tribune columnist that the nation could find itself "irrevocably committed to the socialist path" if Mr Trump lost and that the country faced "a clear fork in the road."

Mr Barr's actions have thrust the Justice Department into the political fray at a time when Democrats and former law enforcement officials have expressed fears that he is politicising the department, particularly by intervening in legal matters in ways that benefit Mr Trump or his circle of friends and advisers.

The protest zone in Seattle became a flash point in the national debate over issues of race and policing this summer. Officers had abandoned the police station there for weeks before retaking it in late July amid escalating violence, including deadly shootings. Ms Durkan said at the time that she had been forced to act because of the lawlessness.

Days later, federal Homeland Security officials sent tactical agents to the city. Ms Durkan protested that their arrival would potentially exacerbate tensions between residents and local officials.

Mr Trump has called the people who lived in the zone "domestic terrorists" and warned that Ms Durkan and Governor Jay Inslee of Washington needed to regain control of the area.

"If you don't do it, I will," the president wrote on Twitter. "This is not a game."

The attorney-general's question about whether Ms Durkan, the former US attorney in Seattle, had violated any federal statutes by allowing the protest zone was highly unusual, former law enforcement officials said.

"The attorney-general seems personally, deeply offended by the autonomous zone and wants someone to pay for it," said Mr Chuck Rosenberg, the former US attorney in the Eastern District of Virginia. "If the people of Seattle are personally offended, they have political recourse. There is no reason to try to stretch a criminal statute to cover the conduct."

His supporters say Mr Barr's approach is necessary to preserve order at a moment that threatens to spiral into violence and to tamp down unrest in cities where the local authorities will not.

More than 93 per cent of the protests in the United States this summer were peaceful, according to a report by the Armed Conflict Location and Event Data Project, which monitors political upheaval worldwide.

The report looked at 7,750 protests from May 26 through Aug 22 in 2,400 locations across all 50 states and the District of Columbia.

But far-right and far-left groups, as well as looters and rioters, have seized on the protests to commit acts of violence, including deadly shootings - serious crimes that some federal prosecutors said could not be dismissed out of hand as anomalous, particularly as the threat from extremist groups grows.

Two men associated with Boogaloo, a far-right movement that supports the coming of a second civil war, were arrested on terrorism-related charges last week. Prosecutors said they used the protests as cover to try to sell weapons to the Palestinian militant group Hamas, which the United States and other countries consider a terrorist group, and to use the money to support the Boogaloo movement.

Mr Barr told federal prosecutors on the call that they needed to crack down on rioting, looting, assaults on law enforcement officers and other violence committed during the protests that have continued across the country since Mr George Floyd, a Black man in Minneapolis, was killed in May by the police.

The attorney-general mentioned sedition as part of a list of possible federal statutes that prosecutors could use to bring charges, including assaulting a federal officer, rioting, use of explosives and racketeering, according to the people familiar with the call. Justice Department officials included sedition on a list of such charges in a follow-up email.