Rioting after a fatal traffic accident involving a U.S. convoy has spread in the Afghan capital today amid reports American troops fired on a rioters, killing one.

Police and eyewitnesses say U.S. and Afghan security forces fired on protesters in Kabul after the accident, which killed three people.

The U.S. says it's investigating.

Hundreds of protesters marched on the palace of U.S.-backed President Hamid Karzai in the city center after the incident, shouting "Death to Karzai! Death to America!"

Elsewhere in the city, gunfire was heard near the U.S. embassy.

The staff was moved to a secure location within the heavily fortified compound.

Rioters broke into shops and stole household items, and an AP reporter said he saw several demonstrators pull a foreign man from a vehicle and beat him.

The man managed to escape.