MIAMI — Four elderly American men pleaded not guilty Wednesday to charges that they were members of a far-right militia which US prosecutors allege had plans to attack government targets, a spokesman said.

"They entered their pleas at a bond hearing at a federal courthouse in north Georgia, Gainesville," said Patrick Crosby, a spokesman for the US Attorney's Office for the Northern District of Georgia, confirming their denials.

"This process, the bond hearing, will continue on Tuesday 15 (November)," but the four men, whose ages range from 65 to 73, will remain in custody, he added.

The men were arrested by FBI agents on November 1.

An undercover FBI informant said in an affidavit that at one meeting of the group Frederick Thomas, 73, "began discussing overt and covert operations" and even proposed destroying a government building like Timothy McVeigh.

McVeigh, a US army veteran and anti-government militia sympathizer, detonated a truck bomb outside a federal building in Oklahoma City in 1995, killing 168 people. He was executed in June 2001 for what was the deadliest terrorist attack on US soil prior to the September 11 attacks later that year.

The FBI informant infiltrated meetings that the suspects -- described in the affidavit as "members of a fringe group of a known militia organization" -- had held starting in March to discuss the attacks.

Thomas mentioned a novel "in which an anti-government group killed a large number of federal Department of Justice attorneys, and then he stated, 'Now of course, that's just fiction! but that's a damn good idea,'" the informant said.

Thomas also spoke of the need to acquire more weapons, ammunition, food, and survival gear, and suggested buying silencers for handguns, it is alleged.

In March and April, Thomas and two other suspects -- Dan Roberts, 67, and Ray Adams, 65 -- discussed targeting government officials, including Internal Revenue Service (IRS) agents.

Adams, who had worked as a laboratory technician at the US Department of Agriculture, is accused of trying to help the fourth suspect, Samuel Crump, 68, try to obtain the biological toxin ricin for the attacks.