A Georgia rural monument that some conservative Christians have criticized as satanic and others have dubbed "America's Stonehenge" was demolished after one of the four granite panels was destroyed in a bombing early Wednesday morning.

The Georgia Bureau of Investigation said the Georgia Guidestones monument near Alberton was damaged by an explosive device and later dropped a pile of rubble "for security reasons", a photo released by investigators.

Surveillance footage showed a sharp explosion turning a panel into rubble after 4 p.m. Investigators have also released video of a silver sedan leaving the monument.

Chris Kubas, executive vice president of the Albert Granite Association, said video cameras attached to the county's emergency dispatch center had been installed at the scene after the earlier vandalism.

The mysterious roadside attraction was created from local granite in 1980, commissioned by an unknown person or group under the pseudonym RC. Christian.

The 16-foot-high (5-meter-high) panels carry a 10-part message in eight different languages, including guidelines for living in “age of reason”. One part called for keeping the world's population at 500 million or less, while the other called for "intelligent reproduction - improving fitness and diversity".