The blast occurred near a hotel in the upscale Shahr-e-Naw neighbourhood, a commercial hub that houses major office buildings, shopping centres, and several embassies.
The area is widely regarded as one of the safest parts of the city.
The Italian NGO Emergency, which operates a hospital in Kabul, said it received 20 casualties following the explosion.
“Among those brought to our surgical centre, seven were dead on arrival,” the organisation said in a statement.
Security forces cordoned off the area as investigations began into the cause of the explosion. No group has so far claimed responsibility for the attack.
The incident has once again raised concerns over security in the Afghan capital, even in areas considered relatively secure.