Police said one contractor was wounded in the attack, The New York Times (NYSE:NYT) reported. The bomber used a taxi to get close to the contractors' convoy.

The victims included a passenger on a minibus and a man pushing a wheelbarrow loaded with firewood.

A few hours after the morning attack, U.S. soldiers killed another man nearby in what military officials said was "an unfortunate incident" caused by the accidental discharge of a weapon into a crowd. Another man was wounded.

Farhad Sherzad, who keeps a shop in the area, told The Times the victim had just bought soft drinks and a phone card. He said the man was sitting on a bench with his cell phone when he was killed.

The suicide bombing was one of about 50 in Afghanistan this year and the fifth in Kabul, where the heavy police and military presence makes them less common.

"The suicide bombers hate Americans but they end up killing ordinary people," said Rahmatullah, a lumber seller in the area.