Three American soldiers were killed and 20 wounded in Afghanistan Wednesday when a B-52 bomber missed its target. The friendly fire incident marked the worst U.S. casualties of the war to date, the Associated Press reported. The Pentagon initially reported that two soldiers were killed. A Pentagon spokeswoman later said one of the injured soldiers had died en route to a hospital. An unknown number of opposition fighters also died in the incident north of the last Taliban stronghold of Kandahar, said a Pentagon spokesman. The troops were hit at about 12:30 a.m. EST (10 a.m. local time) when a B-52 flying a bombing raid dropped a bomb "in close proximity to friendly forces," said a Pentagon statement. Casualties were evacuated to a Marine base in southern Afghanistan for transfer to a medical facility outside the country, said Marine Capt. David Romley. A number of anti- Taliban injured also were being treated at the base.