The FBI warned Monday that armed far-right extremist groups are planning to march on state capitals this weekend, triggering a rush to fortify government buildings amid concerns that the violence that erupted at the U.S. Capitol last week could spread throughout the country.

The memo is something of a raw intelligence product, compiling information gathered by the bureau and several other government agencies, an official said. Some of it is unverified, and the threat is likely to differ significantly from place to place, though the memo said there were plans in all 50 state capitals, said the official, who spoke on the condition of anonymity because the bulletin is considered a law enforcement document not authorized for wide public release.

But the data points it highlights for law enforcement are nonetheless troubling — including that there was information suggesting people might storm government offices, or stage an uprising were President Trump to be removed from office, the official said.

The Post’s Devlin Barrett outlines the potential charges President Trump and his legal team may face for inciting a mob to breach the U.S. Capitol on Jan. 6. (The Washington Post)

The FBI declined to comment on the memo, which was first reported by ABC News. “Our focus is not on peaceful protesters, but on those threatening their safety and the safety of other citizens with violence and destruction of property,” the agency said in a statement.

Officials in many states had already begun taking steps to increase security and plan for additional violence in response to protests last week. On Monday, Wisconsin Gov. Tony Evers (D) announced that he was activating the National Guard to provide support for the Capitol Police in Madison. The troops are members of the Wisconsin National Guard Reaction Force and are trained to quickly deploy in a crisis.

On Saturday, heavily armed demonstrators surrounded the Kentucky Capitol. The protesters, dressed in camouflage and carrying assault weapons and zip-tie handcuffs, vowed to continue to support Trump while railing against Gov. Andy Beshear (D) and Senate Majority Leader Mitch McConnell (R-Ky.).

At a news conference Monday, Beshear vowed he would not be “intimidated,” and he called on Americans to reject those who threaten the symbols and buildings that represent the country’s democratic principles.

“These are not the actions of people who believe in this country. These are people who believe they can bully and intimidate other individuals,” Beshear, visibly angry, said. “To anybody who believes that domestic terror is the way to go, we will be ready for you. We will not back down.”

In Wisconsin, state workers on Monday began boarding up ground-level windows of the Capitol in Madison in anticipation of the protesters. In Arizona, officials had erected a double-layer chain-link fence around the Capitol complex in Phoenix. In Michigan, a state that has been on edge since the FBI disrupted a plot in October to kidnap Gov. Gretchen Whitmer (D), a state legislative committee voted Thursday to ban residents from openly carrying guns inside the Capitol in Lansing.

Washington Gov. Jay Inslee (D) called up 750 National Guard troops to help protect the Capitol, where the legislature kicked off its annual session Monday.

“We sincerely hope for peaceful actions but if that does not happen, we will be prepared,” Inslee said in a statement Friday.

Inslee’s action followed last week’s mob assault on the governor’s mansion, on the same day that a pro-Trump mob stormed the U.S. Capitol, resulting in the deaths of five people including a Capitol Police officer. A video of the disturbance in Olympia, Wash., shows a man with an assault rifle and a large knife standing in front of Inslee’s residence, as other demonstrators stand nearby holding Trump flags.

On the same day in Phoenix, a group of people who were upset about Trump’s loss banged on the locked doors of the Capitol building, cracking a window while shouting for Gov. Doug Ducey, a Republican who has come under fire from conservatives who say he didn’t do enough to help Trump win the state. Besides the new fencing, a spokesman for the Arizona Department of Public Safety said the agency is limiting public access to government buildings. State employees have been encouraged to work from home.

Meanwhile in Oregon last week, demonstrators burned an effigy of Gov. Kate Brown (D). And on Sunday, according to Beshear, someone vandalized the home of Kentucky’s public health commissioner by spray-painting “covid is PCR fraud” on his mailbox.

“This is about individuals, and those bullies trying to create terror by saying we know where you live,” Beshear said.

Alex Friedfeld, an investigative researcher at the Anti-Defamation League’s Center on Extremism, said there remains considerable volatility surrounding who plans to demonstrate at state capitol buildings on Sunday.

Friedfeld said members of the “boogaloo boys” movement — a loose network of anti-government groups who believe the country is heading toward a civil war — began advertising the state capital events in November.

In recent days, Friedfeld has seen signs that supporters of the boogaloo boys appear to distancing themselves from the protests, even calling for the outright cancellation of a march that had been scheduled for Sunday in Washington.

But Friedfeld cautions that the events in the states could still become venues that other extremist groups or random aggrieved Trump supporters latch onto, even though he has yet to see a lot of online chatter that would indicate the protests will be well-attended.

“I have not seen people talking about storming the capitols, but that sentiment is still there and it is possible people show up,” Friedfeld said. “And if the events of Wednesday taught us anything, it is that we can’t ignore right-wing events, and we just can’t assume it will be nothing, and we have to take these things seriously.”

And irrespective of how many and in what states protests materialize this weekend, Friedfeld said he worries that state capitals will continue to be front lines of the country’s bitter, and increasingly violent, cultural and political battles.

He noted that this week’s events represent an escalation of unruly protests that began in some state capitals more than a year ago when gun owners, upset by proposed restrictions on the sale of firearms, began aggressively challenging state leaders in Virginia and elsewhere.

In the spring, conservative activists held demonstrations at state capitols to protest government orders and closures related to the coronavirus pandemic, some of which turned violent. The threats to public safety took an even more ominous turn this fall after the FBI uncovered the plot by far-right extremists to kidnap Whitmer, as well as Virginia Gov. Ralph Northam (D).

“I think people are paying more attention to what is happening at the state level in a way that they didn’t in the past,” Friedfeld said. “And part of what we see with right-wing extremists is, when President Trump took over, they liked President Trump so they kind of shifted ire away from President Trump and toward state and government officials.”

Brian Moran, secretary of public safety in Virginia, said state authorities are bracing for the possibility of large and potentially violent demonstrations both on Sunday — when social media has suggested that the Proud Boys and other groups will show up in Richmond — and Monday, when gun rights advocates are planning a major vehicle caravan through Richmond.

“We have to discern what’s credible or not, but we’re taking it all very seriously,” Moran said.

Moran said law enforcement officials are gathering intelligence to understand what threats the capital might face in the coming days, with the General Assembly convening its legislative session Wednesday. The House of Delegates will meet online, via video conference, but the state Senate will meet in person in a hall at the Virginia Science Museum.

Moran said monitoring has been hampered by the recent crackdown on extremist agitators by social media companies.

“That’s a two-sided coin. It impedes their ability to organize, but also eliminates our eyes on what they are planning,” Moran said. “It requires them to go underground further.”

In Maryland, Greg Shipley, a spokesman for the Maryland State Police, said his agency has also enhanced security at the State House in Annapolis due to posts circulating online about the possibility of armed demonstrations.

“We continue to coordinate with local, state and federal authorities regarding any threats related to the General Assembly session, this weekend or the inauguration,” Shipley said.

Some Republican lawmakers also have been urging the leaders of their states to take the threat of mass rebellion seriously. Jim Steineke, the Republican majority leader of the Wisconsin State Assembly, drew criticism last week when he compared the siege on the U.S. Capitol to the 2011 protests in Madison, where teachers and union workers occupied the Capitol building.

“Learn the lessons from Wisconsin when liberal throngs stormed the State Capitol and took it over. If you do not clear them now, you will lose control for days if not weeks,” Steineke wrote on Twitter.

But amid the tightening security, some state lawmakers say they are worried that the threats they now face will persist long after this weekend.

Michigan state Rep. Donna Lasinski (D) noted how she was approaching her office Thursday morning when she received a text alert that the building was being evacuated because of a bomb threat.

Lasinski recounted how she froze, uncertain whether to go inside where state police were standing or run away.

“What I know is it has become untenable for folks, lawmakers, staff, school groups to feel that they can come to our state Capitol, to the people’s house, and feel that they won’t be threatened or harassed or intimidated,” she said. “This cannot be our new normal.”

Erin Cox, Ovetta Wiggins and Gregory S. Schneider contributed to this report.