The FBI says it has thwarted a plot to abduct and overthrow Michigan's Democratic Governor Gretchen Whitmer.
Mrs Whitmer has become a target for coronavirus sceptics after enacting strict measures that were overturned by a judge last week.
Officials say the kidnapping plot involved six men who planned to hold a "treason trial" for her.
"Hatred, bigotry and violence have no place" in Michigan, Mrs Whitmer said, describing the accused as "depraved".
What were they allegedly planning?
According to a sworn FBI affidavit, an undercover law enforcement source attended a June meeting in Dublin, Ohio, where a group of Michigan-based militia members discussed overthrowing state governments "that they believed were violating the US Constitution".
"Several members talked about murdering 'tyrants' or 'taking' a sitting governor," the charging document states. In one video, a suspect denounced the state's role in deciding when to reopen gyms during the coronavirus lockdown.
The men met in a basement that was accessed by a trapdoor hidden under a rug, investigators say. Their phones were gathered and placed in another room to avoid secret recordings, but the undercover FBI source was wearing a separate recording device.
Thirteen people were arrested by investigators.
Six men - five from Michigan and one from Delaware - are accused in federal court of plotting the kidnap. They allegedly planned to hold a "treason trial" against Mrs Whitmer.
These six were named as Adam Fox, Barry Croft, Kaleb Franks, Daniel Harris, Brandon Casert and Ty Garbin. Mr Garbin's residence, in a trailer park, was raided by authorities on Wednesday.
The other seven face charges of terrorism and gang-related offences in state court in connection with the alleged abduction plot.
They are Paul Bellar, Shawn Fix, Eric Molitor, Michael Null, William Null, Pete Musico and Joseph Morrison.
The group wished to gather about "200 men" to storm the capitol building and take hostages, including the governor. They hoped to enact their plan before the November presidential election. If that failed, they planned to attack the governor at her home, officials say.
The accused "co-ordinated surveillance of the governor's vacation home", said the US Attorney for the Western District of Michigan, adding that they also planned Molotov cocktail attacks on police officers, purchased a taser, and pooled their funds to purchase explosives and tactical equipment.
What do we know about the group?
The accused held weapons training in several states, and at times attempted to create bombs, the FBI says, adding that their training was captured on video.
Michigan Attorney General Dana Nessel said that separate to the kidnapping charges seven members of the "wolverine watchmen" militia will be charged by the state with gang affiliation and providing material support to terrorists. Ms Nessel said the arrested militia members hoped to start a civil war.
Social media's Boogaloo problem
It's been reported that these men have links to a militia group called the Boogaloo Bois. This is a movement that has grown online.
It's actually quite hard to describe the motives of the group. It's not "right-wing" in a traditional sense. Members of the movement are vehemently against law enforcement - some have been arrested for killing police officers.
Broadly speaking, they are extremist libertarians - think Timothy McVeigh, the Oklahoma City bomber, but with guns.
The term "Boogaloo" is usually a reference to a civil war. They have an entrenched hatred of big government - confusingly they are also often pro-Trump, though not exclusively. Hence why their ire is often focused on state rather than federal government.
Social media took a long time to act on Boogaloo. Facebook removed a number of Boogaloo groups in June - including the group that these men were allegedly part of. I showed TikTok of a series of Boogaloo videos that were on its platform back in July. Even now it's very easy to find Boogaloo videos on social media - the hashtags they use often change so it's hard to keep up.
This story shows how important it is to monitor social media platforms for extremist content - before it leads to violence.
"Michigan law enforcement officers are united in our commitment to rooting out terrorism in any form and we will take swift action against anyone seeking to cause violence or harm in our state," Colonel Joe Gasper, director of the Michigan State Police, said in a statement announcing charges against the "wolverine watchmen".
What has the governor said?
In a press conference on Thursday, the governor tied the plot against her to the rhetoric of President Donald Trump, who she said had spent the last several months "stoking distrust, fomenting anger and giving comfort to those who spread fear and hatred and division".
In April, Mr Trump implied support for the protesters, tweeting "LIBERATE MICHIGAN". A month later, armed protesters opposed to the lockdown stormed the state capitol.
Michigan's attorney general confirmed on Thursday night that two men photographed at that May protest are among the arrested plot suspects.
On Thursday night, Mr Trump, a Republican, sought to take credit for federal investigators eliminating the alleged threat to the governor.
"Rather than say thank you, she calls me a White Supremacist - while Biden and Democrats refuse to condemn Antifa, Anarchists, Looters and Mobs that burn down Democrat run cities," he tweeted.
The Midwestern state of Michigan could prove pivotal in the outcome of next month's US presidential election.
Joe Biden, the Democratic White House challenger to Mr Trump, condemned militias as "a genuine threat" and said Mr Trump's "liberate" tweet encouraged militias. "The words of a president matter," he said, adding: "Why can't the president just say stop, stop, stop, stop?"
Numerous violent incidents have been linked to citizen militia groups across the US in recent years. Adherents, who are often white men, sometimes brandish weapons during protests. The Department of Homeland Security warned this week in an annual report that violent white supremacy was the "most persistent and lethal threat in the homeland".
Mrs Whitmer's lockdown orders drew thousands of protesters to the state capitol, where many compared her to German dictator Adolf Hitler.
"None of us has faced a challenge like Covid-19," Mrs Whitmer said on Thursday. "We are not one another's enemy. This virus is our enemy, and this enemy is relentless."
Last Friday, the state's Supreme Court ruled that Mrs Whitmer did not have the legal authority to issue emergency executive orders and that that responsibility belonged to the state's legislature.
Following the ruling, the attorney who argued the case before the top court advised citizens to "burn your masks", which health officials say are necessary to prevent the spread of Covid-19.