Kabul: A NATO convoy was attacked near the parliament building in the Afghan capital on Friday, police and the coalition said, the first attack in Kabul in three months months after security was increased.
There was no immediate word on casualties.
Afghan authorities clamped a "ring of steel" across the city before parliamentary elections in mid-September, with checkpoints manned by armed police still in place across parts of Kabul.
While the capital had been relatively quiet, violence across the rest of Afghanistan has reached its worst level since the Taliban were overthrown by U.S.-backed Afghan forces in 2001 despite the presence of about 150,000 foreign troops.
Civilian and military casualties are at record levels.
A police source said Friday`s attack had been carried out by a suicide bomber, although a spokesman for the NATO-led International Security Assistance Force (ISAF) said it appeared to have been a roadside bomb.
Neither police nor ISAF had any immediate word on possible casualties.
The Taliban had vowed to disrupt the September 18 vote but the ballot went ahead, although attacks were reported across the country on polling day and 17 people were killed.
One rocket fired by insurgents landed in Kabul in the pre-dawn hours of election day but caused no major damage or injuries.
The last serious attack in Kabul was on August 10, when two suicide bombers killed up to five Afghans in an attack on a residential area of central Kabul. One of the suicide bombers blew himself up at the gate of a compound used by foreigners.