The attacker detonated his vehicle in a busy part of western Kabul, said interior ministry spokesman Sediq Sediqqi. Two children and one woman were among the dead, a police statement said, while some 35 others were wounded.
Local TV footage showed at least one ISAF military vehicle was slightly damaged in the attack. A spokesman for the NATO-led force in the country said they were looking into the incident but did not comment on the details.
Taliban spokesman Zabihullah Mujahid claimed responsibility for the attack.
On Tuesday, a US general was killed and over a dozen others were wounded when an Afghan soldier turned his gun on their delegation.