The blast took place last night outside a football ground in impoverished Layari area which has a tradition of holding soccer matches in Ramadan.
The bomb was detonated near the vehicle of Javed Naghori, a provincial minister who was leaving after witnessing a match between two local teams, a police officer said.
Naghori escaped unharmed. Seven persons were killed in the blast, mostly teenagers.
"We are investigating the bombing," the officer said.
Last night four small explosion were also reported from different parts of the city.
Violence has increased since new government was formed after May 11 elections.