Four American soldiers have been charged in a plot to overthrow the government and assassinate President Barack Obama, marking one of the most credible and high-profile plots on his life since his election in 2008.

The soldiers, based in Georgia, allegedly planned to take over the state's Fort Stewart and carry out bombings in Savannah and Washington state using $87,000 worth of "guns and bomb-making materials" they had allegedly amassed, according to the Atlantic Wire.

The Daily Beast reports that prosecutors said the group's bombing targets included a famous fountain in one of Savannah's gracious parks and a dam in Washington, and that they also planned to poison a Washington state apple crop.

But the ambitious plans were uncovered during testimony Monday in the course of an investigation into the Dec. 4 killings of former soldier Michael Roark and his 17-year-old girlfriend Tiffany York after they became aware of the group's plot, according to the Associated Press.

All four of the defendants are being held on charges of malice murder, felony murder, criminal gang activity, aggravated assault and using a firearm while committing a felony in connection with their alleged scheme, the AP reported on Monday after news of the plot broke.

On Monday, one of them, Army Pfc. Michael Burnett, pleaded guilty to manslaughter and illegal gang activity in connection with the murders of Roark and York, the AP said.

He said the four soldiers took the couple into the woods near Fort Stewart and shot them to death in order to prevent their grandiose plans from being exposed, according to the AP

"Burnett told a Long County judge that Roark, who had just left the Army, knew of the militia group's plans and was killed because he was 'a loose end,'" the AP wrote Monday.

The plotters were allegedly members of a right-wing extremist group called F.E.A.R., which stands for Forever Enduring Always Ready, according to the AP. The case has parallels to a report that came out last week in Reuters about American extremists allegedly joining the military "to acquire the skills to overthrow what some call the ZOG - the Zionist Occupation Government. Get in, get trained and get out to brace for the coming race war."