A suicide car bomb exploded outside the main gate of the Nato-led military mission in Kabul yesterday, killing four Afghans and wounding 91.

The attack penetrated a heavily guarded neighbourhood just 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.

Militants have warned Afghans not to vote and have threatened to attack voting sites.

The Nato headquarters sits beside the US 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 was 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. US, 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 the blast. Children – many of whom congregate outside the Nato gate to sell gum to westerners – were among the wounded.

The Taliban claimed responsibility and said the target was the Nato headquarters and the US embassy some 150 yards down the street. A top Kabul police official blamed al-Qaeda.

Brig Gen E Tremblay, the spokesman for the Nato-led force, said the Taliban was "indiscriminately killing civilians".

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

A Taliban spokesman, Zabiullah Mujahid, claimed responsibility for the blast and said the bomb contained 1,100lbs of explosives. Mujahid at first said the bomber was on foot, then later 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 has carried out several coordinated attacks in the last few months with multiple teams of insurgents assaulting government sites.

Mujahid said a suicide bomber named Ahmadullah from the Bagrami district of Kabul province carried out the attack.