KABUL: A suicide car bomb exploded outside the main gate of the NATO-led military mission Saturday, killing four Afghans and wounding 91 in an attack that penetrated a heavily guarded neighborhood five days before the country's presidential election.

The bomber evaded several rings of Afghan police and detonated his explosives at the doorstep to the international military headquarters, an assault possibly aimed at sending the message that the Taliban can attack anywhere as Afghans gear up for their second-ever direct presidential election. Militants have warned Afghans not to vote and have threatened to attack voting sites.

The NATO headquarters — where top commander U.S. Gen. Stanley McChrystal is based — sits beside the U.S. Embassy and shares the same street as the presidential palace. The explosion was the first major attack in Kabul since February, when eight Taliban militants struck three government buildings simultaneously in the heart of the city, an assault that killed 20 people and the eight assailants.

Afghanistan has braced for attacks ahead of the election. International workers in the country were planning on working from home over the next week or had been encouraged to leave the country. U.S., NATO and Afghan troops were working to protect voting sites, particularly in regions where militants hold sway.

Bloodied and dazed Afghans wandered the street after Saturday's blast, which rattled the capital and sent a black plume of smoke skyward. Children — many of whom congregate outside the NATO gate to sell gum to Westerners — were among the wounded. Windows of nearby antique shops were shattered and blood smeared the ground.

The Taliban claimed responsibility and said the target was the NATO headquarters and the U.S. Embassy some 150 yards (meters) down the street. A top Kabul police official blamed al-Qaida.

Brig. Gen. E. Tremblay, the spokesman for the NATO-led force, said some soldiers in the International Security Assistance Force were wounded in the 8:35 a.m. blast. He did not say how many. The explosion occurred 30 yards (meters) from NATO's front gate, he said. Pointing to the civilian casualties, Tremblay said the Taliban were "indiscriminately killing civilians."

Afghan security forces stopped the vehicle in front of NATO headquarters, and then the bomber detonated the explosives, Tremblay said.

The blast killed four Afghans and wounded 91, Gen. Mohammad Zahir Azimi, the spokesman for the Afghan Ministry of Defense, said.

Four Afghan soldiers and Awa Alam Nuristani, a member of parliament and President Hamid Karzai's campaign manager for women, were among the wounded, 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 sustained 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.

A Taliban spokesman, Zabiullah Mujahid, claimed responsibility for the blast and said the bomb contained 1,100 pounds (500 kilograms) of explosives. Mujahid at first said the bomber was on foot, then later called back and said it was a suicide car bomb attack.

The attack falls in line with increasingly spectacular and sophisticated strikes carried out by Afghanistan militants. The Taliban have carried out several coordinated attacks in the last several months with multiple teams of insurgents assaulting government sites. Military analysts have said the increased sophistication comes from training by al-Qaida operatives.

NATO headquarters has several large, cement blocks and steel gates that prevent anyone from reaching the entrance, and the bomber was not able to breach those barriers. Afghanistan's Transportation Ministry lies across the street from NATO headquarters.

Mujahid, the Taliban spokesman, said a suicide bomber named Ahmadullah from the Bagrami district of Kabul province carried out Saturday's attack.

A driver from the nearby Defense Ministry said he took at least 12 people to the hospital. Most were seriously wounded, said the driver, who spoke to an Associated Press reporter at the scene but didn't want to give his name because of safety concerns.

Kabul has been relatively quiet over the last half year, though militants have launched a barrage of rockets into the capital this month, most of which landed harmlessly in open spaces.

Security has increased over the last several weeks in preparation for Thursday's vote.