The improvised explosive device (IED) was reportedly planted by militants in the fifth district of Kabul.
More than a dozen other civilians, including women and children, were also injured in the Tuesday bombing.
The target of the bomb attack was reportedly an Afghan security convoy.
No group or individual has claimed responsibility for the attack. However, authorities in Kabul have blamed the Taliban militant group for similar assaults in the past.
Afghan children are bearing the brunt of the violence in Afghanistan. A report by the United Nations in June showed that the death toll among Afghan civilians, especially children, had increased dramatically due to widespread violence in the country.
Over the past few months, Afghan security forces have stepped up offensives against militant hideouts across the country.