KANDAHAR: International troops opened fire on a bus carrying Afghan civilians early Monday, killing four people and setting off anti-American protests in Kandahar.

Another 18 people were wounded in the incident in Kandahar’s Zhari district, provincial government spokesman Zelmai Ayubi said. He said international forces took 12 of the wounded to a military hospital. NATO said it was investigating the shooting.

Within hours, scores of Afghans had blocked the main highway out of Kandahar city with burning tires, chanting “Death to America,” and calling for the downfall of Afghan President Hamid Karzai, himself a Kandahar native.

“The Americans are constantly killing our civilians and the government is not demanding an explanation,” said resident Mohammad Razaq.

“We demand justice from the Karzai government and the punishment of those soldiers responsible.”

Afghan civilians said the convoy that fired on the bus was American, although NATO and Afghan authorities declined to identify them by nationality. Razaq and others claimed the bus was fired on merely because it had pulled up close behind the convoy.

Kandahar spokesman Ayubi said the provincial government strongly condemned the shooting. NATO spokesman Mst. Sgt. Jeff Loftin said the alliance had dispatched a team to the scene to investigate, but didn’t say whether its troops were responsible for the shooting.

Loftin said the local command in Kandahar had no further information on what had