( AFP ) - A suicide bomber blew himself up near a convoy of foreign troops in the Afghan capital early Tuesday and initial reports said several people had been wounded, a government official said.
US Defence Secretary Robert Gates arrived in the capital late Monday for a surprise visit.
"There was a suicide car bomb on the airport road against foreign troops," interior ministry spokesman Zemarai Bashary told AFP.
"It is said that some people have been injured but at this point we don't have an exact number of casualties," he said on Monday.
The NATO-led International Security Assistance Force confirmed the explosion.
"We know there was a suicide car bomb but we don't have casualties and I can't confirm that ISAF was the target," spokesman Lieutenant Colonel Thomas Dillschneider said.
The separate US-led coalition was not immediately available for comment.
It was not initially clear who was responsible for the blast. There have been about 140 suicide attacks in Afghanistan this year, most carried out by the extremist Taliban movement that was in government between 1996 and 2001.
Gates arrived for a short trip during which he was to meet President Hamid Karzai later in the day as well as visit ISAF commanders to evaluate international efforts to fight the increasing Taliban insurgency.