He said six of those aboard were killed and four wounded.
Afghan troops could be seen carrying wounded civilians to ambulances near the wreckage of a military vehicle bearing the insignia of the Nato-led International Security Assistance Force (Isaf).
Al Jazeera's Zeina Khodr, reporting from Kabul, said the Taliban have claimed responsibility for the attack.
"[They said] the purpose is to show that there is no where safe in Afghanistan.
"We were at the site of the explosion mid-morning. There was a lot of chaos.
"The situation is deteriorating, with violence really at an all time high.
"As violence continues people are concerned about the security situation and the political uncertainty in this country."
Our correspondent said the blast marked the fourth major attack in the capital in five weeks.
On September 8, at least three civilians died in an attack targeting a Nato convoy near the entrance to the military airport in Kabul.