The army provided no details on the nature of the accident, which is under investigation, except to say it occurred during an exercise at Fort Stewart, Georgia.

"Six soldiers were involved, with three pronounced deceased on site, and three more evacuated to Winn Army Community Hospital where they are being treated and evaluated for their injuries," an army statement said.

Major General Tony Aguto, commander of the 3rd Infantry Division, called it a "heartbreaking day."

The soldiers, who were in a Bradley Fighting Vehicle, were from the 1st Armored Brigade Combat Team.