The Taliban quickly denied it was behind in the attack in Kabul's Macrorayan neighborhood, though the militants increasingly have been targeting Kabul in recent weeks and often don't claim attacks that maim large numbers of civilians.
The attack struck near the private Shinozada hospital, the sound of the powerful blast roaring throughout the capital. Ambulances and Afghan security forces quickly surrounded the blast site, blocking access off from about 1 kilometer (half a mile) away.
It was not immediately possible to reconcile the differing casualty figures, though conflicting information is common after such attacks.
At least one armored vehicle in the convoy had been destroyed by the blast. It wasn't clear how many armored cars were in the convoy, though it is at least two, often three because of heightened security concerns in the capital.
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Najib Danish, a deputy Interior Ministry spokesman, said the attack destroyed more than a dozen civilian vehicles parked in the street and passing by.
"A lot of dead bodies and wounded victims were there after the explosion happened in the area," said Mohammad Hussain, who was wounded in the attack. "There were a lot of casualties."
No group immediately claimed responsibility for the attack. In an email to journalists, Taliban spokesman Zabiullah Mujahid denied his group was responsible.
Their targets have included foreign military and civilian convoys.