Flames shot into the sky after a homicide car bomber attacked an American military convoy on the road to Kabul's airport Saturday, killing a U.S. soldier and four Afghan civilians, officials said.

The bombing — on the sixth anniversary of the U.S.-led invasion of Afghanistan — threw several vehicles on their side. Four Afghans were killed and several others wounded, the Interior Ministry said.

The attack was against U.S. troops responsible for training the Afghan military and police. Lt. Col. David Johnson, a U.S. spokesman, said one American soldier died in the blast and one was wounded.

Dozens of shops were damaged.

"There was an enormous explosion, the windows of my shop shattered," said tailor Mohammad Isaq. "When I came out I saw the foreigners' vehicles on fire. I saw two injured Afghans and I ran to help them."

Saturday was the sixth anniversary of the U.S.-led invasion to oust the Taliban for hosting Al Qaeda leader Usama bin Laden following the Sept. 11, 2001, terrorist attacks on the United States.

This year has been the most violent of the six-year effort. More than 5,100 people have died in insurgency-related violence in 2007, according to an Associated Press count based on Afghan and Western officials.

The homicide bombing was the third major attack in Kabul in a week. On Sept. 29, a bomber targeted an Afghan army bus, killing 30 people. A similar attack Tuesday against a police bus killed 13.

Saturday's attack occurred on a tree-lined, four-lane road that leads from the U.S. Embassy to the airport — a route frequently traveled by foreign convoys.

U.S. military Humvees arrived at the scene shortly after the 8:15 a.m. (0315 GMT) bombing to secure the site and take away U.S. casualties. British troops arrived soon after that.