A Reuters television team counted eight people who appeared to have been killed, besides several wounded at the scene, which was shrouded in smoke from the explosion. All the casualties appeared to be Afghan civilians.
A public health official said three dead and 10 wounded had been taken to city hospitals.
There was no immediate claim of responsibility, or confirmation of the cause of the explosion. A Kabul police spokesman said it appeared to have been caused by a suicide bomber on foot but police were also investigating whether it was a bomb planted earlier.
The street in the Wazir Akbar Khan area of the city is close to several foreign embassies, as well as an office and guesthouse of the ministry of defence.
The blast follows a series of attacks in or around Kabul this month, including one on a Shi'ite mosque in the city that killed more than 50 people and a separate attack on an army training facility that killed at least 15 soldiers.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)