The attack follows several weeks of relative quiet in Kabul and there was no immediate claim of responsibility.
The blast appeared to have been caused by a suicide bomber and had caused casualties but there were no immediate details.
An official from the ministry of public health said ambulances returning from the site had brought at least four dead and 15 wounded into city hospitals but the final toll was not known.
Voter registration centres have been set up across Afghanistan in preparation for long-delayed parliamentary elections due to be held in October and there have been serious concerns that they could be targeted by attacks.
