The blast, which occurred about 8:35 a.m. in Kabul's heavily guarded diplomatic quarter, appeared aimed at frightening Afghans against participating in Thursday's presidential election and demonstrating that insurgents can strike whenever and wherever they want.
A Taliban spokesman claimed responsibility for the explosion, which rattled windows across a wide area of the Afghan capital and send a huge, mushroom cloud of dense black smoke rising into the blue sky.
It was the biggest insurgent attack in Kabul in six months and shook public confidence in the extensive network of checkpoints and armed guards that maintain security in the city.
The bomber managed to evade several rings of Afghan police and detonated his vehicle about 30 yards (meters) from the main entrance to the NATO base, where top U.S. commander Gen. Stanley McChrystal has his headquarters. It was unknown whether McChrystal was there at the time of the attack.
After the blast, bloodied and dazed Afghans wandered the street. They included children who congregate outside the NATO gate to sell gum to Westerners. Windows of nearby antique shops and diplomatic residences were shattered and blood smeared the ground.
President Hamid Karzai blamed the attack on the "enemies of Afghanistan" who were "trying to create fear among the people as we get close to the election," in which Karzai is favored to win a second, five-year term.
Karzai said in a statement that Afghans "are not afraid of any threats, and they will go to cast their votes."
Taliban spokesman Zabiullah Mujahid claimed responsibility and said the target was the NATO headquarters and the U.S. Embassy about 150 yards (meters) down the street. A top Kabul police official blamed al-Qaida because of the size of the blast.
Brig. Gen. E. Tremblay, the spokesman for the NATO-led force, said some soldiers in the International Security Assistance Force were wounded in the blast but did not say how many. Macedonia said three Macedonian soldiers who were guarding the gate were slightly injured.
Afghan security forces stopped the vehicle in front of NATO headquarters, then the bomber detonated the explosives, Tremblay said.
"The security measures in place have stopped cold the bombers as planned," he said, calling the latest attack an example of the "residual risk" that remained despite the safety measures taken. "It's very difficult to stop a suicide bomber."
The blast killed seven Afghans and wounded 91, Gen. Mohammad Zahir Azimi, the spokesman for the Afghan Ministry of Defense, said.
Among the wounded were four Afghan soldiers and Awa Alam Nuristani, a member of parliament and Karzai's campaign manager for women, the ministry said.
"I was drinking tea in our office when a big explosion happened," said Abdul Fahim, an Afghan in his mid-20s who suffered leg injuries. "I lay on the ground and then I saw wounded victims everywhere, including police and civilians."
The chief of Kabul's criminal investigation department, Abdul Ghafar Sayadzada, said 600 pounds (272 kilograms) of explosives were used, and that because of the amount he suspected al-Qaida was involved. The attacker passed three police checkpoints, Sayadzada said.
But Mujahid, the Taliban spokesman, said a suicide bomber named Ahmadullah from the Bagrami district of Kabul province carried out Saturday's attack.
It was the first major assault in Kabul since February, when eight Taliban militants struck three government buildings simultaneously in the heart of the city. At least 28 people, including eight assailants, were killed.
Interior Ministry spokesman Zemeri Bashery said police were trying to figure out how the insurgents managed to carry out such an attack in one of the most tightly secured areas of the city. "They must have used a new tactic to carry out this suicide attack," he said. "What kind of tactic we cannot say until the investigation is over."
Mujahid, the Taliban spokesman, brushed aside talk of new tactics but said "we have peoples' support with us, the people are helping us to carry out our attacks."
"We have already announced that the people should not participate in the election," he said. "We have announced that the people should not participate in this American process. We are going to block the highways and roads leading to polling centers and attack those polling centers where we see Americans and other foreigners."
In Dahaneh, Marines launched a pre-dawn raid against a Taliban position on the southern edge of the town, storming a fortified compound and then blowing up two towers from which insurgents fired rockets and mortars at U.S. troops the day before.
Marines found marijuana plants growing in the courtyard and confiscated trigger plates used to manufacture roadside bombs. U.S. troops launched an assault on Dahaneh early Wednesday, hoping to disrupt Taliban supply lines in the Now Zad valley and establish Afghan government control over an area held by the Taliban for years.
Associated Press Writers Amir Shah and Nahal Toosi in Kabul and Alfred de Montesquiou in Dahaneh contributed to this report.