KABUL, Afghanistan (AP) – A suicide car bomber attacked an American military convoy on the road to Kabul’s airport on Saturday, killing a U.S. soldier and four Afghans and sending flames shooting into the sky, officials said.

The bombing – on the eve of the sixth anniversary of the U.S.-led invasion of Afghanistan – threw several vehicles on their side. Four Afghans were killed and 12 wounded, the Health 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.

“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.”

This year has been the most violent of the six-year effort, the result of the U.S.-led invasion to oust the Taliban for hosting al-Qaida leader Osama bin Laden following the Sept. 11 terrorist attacks on the U.S.

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 suicide 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.

President Hamid Karzai condemned the attack and said the violence is forced upon Afghanistan from abroad – a reference to Pakistan, where many Taliban fighters come from.

“In the religion and culture of the Afghan people, there is no place for such wild and un-Islamic attacks, but these kind of conspiracies are pressed onto our people from the outside,” Karzai said in a statement.

Abdul Manan Farahi, Kabul’s counterterrorism chief, said Kabul police in the last six months prevented 156 terror attacks, including 18 suicide bombings. He said one man from Morocco, one from Saudi Arabia and several from Pakistan were among the 18 would-be suicide attackers arrested.

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.

In the south, in Uruzgan province, Taliban fighters attacked an Afghan security company guarding a road construction project, killing five of the security guards, said Kandahar provincial police chief Sayed Agha Saqib. Ten Afghan guards were missing, he said.

Some 40 to 50 fighters in Ghazni province, meanwhile, laid down their arms and joined the government’s reconciliation process, said Kazim Alayar, deputy governor. The fighters are from Andar district, a notorious Taliban stronghold where militants held some of the 23 South Korean hostages kidnapped in July. Ghazni’s new governor, Abdul Manan, comes from Andar.

More than 4,500 fighters have joined the government through the reconciliation process.

In Helmand province’s Gereshk district, a roadside bomb explosion killed a policeman, said Abdul Manaf Kahan, the district chief.

Britain’s Ministry of Defense on Saturday announced the death of Maj. Alexis Roberts, Prince William’s former Sandhurst platoon commander, who was killed in an explosion in southern Afghanistan. Roberts, of the 1st Battalion The Royal Gurkha Rifles, was the highest ranking British officer killed there since operations there began in November 2001, the Ministry of Defense said.

Separately, Japan’s Defense Ministry denied a media report Saturday that it planned to withdraw its naval mission to support U.S.-led troops in Afghanistan on Nov. 1, saying the government expected parliament to approve an extension before then.