By Christina Carrega, CNN

(CNN) -- Six men were charged Thursday in an alleged plot to kidnap Michigan Democratic Gov. Gretchen Whitmer, according to a federal criminal complaint.

The alleged plot included plans to overthrow several state governments that the suspects "believe are violating the US Constitution," including the government of Michigan and Whitmer, according to the complaint.

The FBI became aware of the scheme, first reported by The Detroit News, in early 2020 through a social media group of individuals, according to the criminal complaint.

The arrests are likely to draw additional attention to the political tensions roiling the nation in the closing weeks of the 2020 election season, and underline warnings from law enforcement officials, members of Congress and groups that track extremism about the increasing threat of militia and far-right groups. Whitmer at times has been the focus of extreme vitriol from far-right groups over her handling of the coronavirus pandemic.

The six individuals charged in the Western District of Michigan with conspiracy to kidnap are Michigan residents Adam Fox, Ty Garbin, Kaleb Franks, Daniel Harris, Brandon Caserta, and Delaware resident Barry Croft.

Court documents say the FBI planted an undercover agent to travel to Dublin, Ohio, on June 6 for a meeting with Croft, Fox and about 13 others.

"They discussed different ways of achieving this goal from peaceful endeavors to violent actions ... Several members talked about murdering 'tyrants' or 'taking' a sitting governor," according to the complaint.

At one point during the meeting, the group discussed increasing their members and Fox reached out to a "Michigan base militia group," according to the complaint.

By June 14, a second confidential informant confirmed that Fox was introduced to the leader of the militia group and they met in Grand Rapids, Michigan. The informant audio recorded conversations with Fox in which he allegedly said he needed "200 men" to storm the Capitol building in Lansing and take hostages, including Whitmer, according to the criminal complaint.

While the Capitol has a formal office for the governor, Whitmer works out of an office across the street.

Fox explained they would try the governor of Michigan for "treason" and he said they would execute the plan before the November 2020 elections, according to the criminal complaint.

On June 20, Fox, Garbin and others met at Fox's business in Grand Rapids where attendees met in the basement accessed by a trap door hidden under a rug on the main floor, according to the criminal complaint. Attendees turned over their cell phones, which were brought upstairs to "prevent any monitoring."

"The attendees discussed plans for assaulting the Michigan State Capitol, countering law enforcement first responders, and using 'Molotov cocktails' to destroy police vehicles. The attendees also discussed plans for an additional meeting during the first weekend of July when they also would conduct firearms and tactical training," according to the criminal complaint.

The five defendants who are Michigan residents are expected in court Thursday afternoon. The whereabouts of Croft, the Delaware resident, are unclear.

It wasn't immediately clear if the men had attorneys.

Whitmer is scheduled to deliver remarks Thursday afternoon. Michigan Senate Majority Leader Mike Shirkey, a Republican, strongly condemned the threat against the governor.

"A threat against our governor is a threat against us all," Shirkey said in a statement. "We condemn the actions of the group of individuals that plotted against Governor Whitmer and state government. These people are not patriots. There is no honor in their actions. They are criminals and traitors, and they should be prosecuted to the fullest extent of the law."

Whitmer has been the target of multiple death threats in light of her coronavirus response efforts and decision to issue stay-at-home orders. In April, protesters and militia gathered at the state capitol for a rally, gridlocking the streets to call for Whitmer to lift her stay-at-home order.

At one point in the spring, armed protesters entered the state capitol, where it is legal to openly carry firearms, and demanded an end to Michigan's state of emergency.

This story is breaking and will be updated.