Hafez Khan said police were investigating today's blast, which took place in a residential neighborhood of Kabul, far from any government offices or other obvious targets.
Kabul's deputy police chief, Aqhnawaz Aqyar, later said it appeared to have been an accidental explosion at a shop selling cooking gas canisters.
A bombing in the eastern Nangarhar province earlier in the day killed one person and wounded eight.
Attaullah Khogyani, spokesman for the provincial governor, said the blast took place inside a mosque during Friday prayers.