Staff at the US embassy in Afghanistan have been evacuated after crowds attacked the mission in Kabul. Police fired shots into the air to drive the protesters back. It is thought the incident was linked to unrest earlier which followed a fatal road accident involving a US military convoy. Several people were killed in shooting during a subsequent riot at the scene of the collision.An American embassy spokesman said personnel had been moved to a safe location. In addition to those killed, at least 20 people were injured in the gunfire that followed the traffic accident. It was not immediately clear who was responsible for the initial shooting that broke out as police came to the assistance of the US convoy. It had come under attack from a crowd hurling stones. Some eyewitnesses blamed the US troops, others said the police were at fault, while there were claims both had opened fire. More than 20 Afghans have been killed in anti-Western protests in the past year in the country.