Protests after US troops 'kill four civilians on bus'

The deaths set off protests across the area, a hotbed of Taliban insurgency.

Another 18 people were wounded in the incident in Kandahar province's Zhari district yesterday. Nato said it was investigating the shooting.

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

Resident Mohammad Razaq said: "The Americans are constantly killing our civilians and the government is not demanding an explanation.

"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.

One of the bus passengers interviewed in hospital, Rozi Mohammad, said they had just left the Kandahar terminal when the bus pulled over to allow an American convoy to pass.

Shooting broke out as the third or fourth American vehicle went by, he said, with gunfire coming from the direction of the convoy.

"They just suddenly opened fire, I don't know why. We had been stopped and after that I don't know what happened," said Mr Mohammad, his left eye swollen shut and his beard and clothing matted with blood. Doctors said he had suffered a head injury but did not yet know how serious it was.

Nato said the bus had approached a slow-moving patrol from behind at a high speed and ignored signals to slow down.

"Perceiving a threat when the vehicle approached once more at an increased rate of speed, the patrol attempted to warn off the vehicle with hand signals prior to firing upon it. Once engaged, the vehicle then stopped," Nato said in a statement.

Kandahar spokesman Ayubi said the provincial government strongly condemned the shooting. A Nato spokesman said the alliance had dispatched a team to the scene to investigate, but did not say whether its troops were responsible.

The top Nato commander in Afghanistan, US Gen. Stanley McChrystal, has issued strict orders to his troops to try to reduce civilian

casualties.

Obama warns on nuclear security

If al-Qaida acquired nuclear weapons it "would have no compunction at using them," President Barack Obama warned at the start of this week's summit aimed at finding ways to secure the world's nuclear stockpile.

The Nuclear Security Summit of more than 40 world leaders in Washington is aimed at securing "loose nuclear material", Mr Obama said.

"The single biggest threat to US security, both short-term, medium-term and long-term, would be the possibility of a terrorist organisation obtaining a nuclear weapon."