Police in Kabul have accused foreign troops of firing at a civilian vehicle outside the Afghan capital, killing a young boy.
About 100 people blocked the road near the place where the incident occurred on Friday, throwing rocks at the police while shouting anti-US slogans.
"This morning a convoy of British troops were passing here and they had a misunderstanding with a civilian vehicle. The troops opened fire and killed one civilian and wounded three more," Mohammad Ayoub Salangi, Kabul's police chief, told Reuters news agency.
But the International Security Assistance Force (Isaf) disputed the claim that its troops had opened fire, saying the incident had been a traffic accident.
The US-led coalition said that it regretted the accident, in which one of its vehicles had been hit by a civilian minivan that then crashed into a roadside shop, causing the casulaties.
Crowds chanted "death to Bush, death to America" as the body of the victim was put into the back of a taxi and driven away from the scene.
"They killed my son, my son is dead," said a weeping old man.
The rioters pelted Afghan police with stones and were chased down side-streets before dispersing.