The blast took place on Saturday afternoon when some mechanics were busy in the shop repairing an oil tanker in the provincial capital Ghazni city. The blast killed three on the spot, the official added, Xinhua reported.
Without providing further details, the official said that an investigation is underway to determine the reason for the deadly incident.
Earlier, an explosive device from past wars went off in the Nawar district of Ghazni province, killing two children and injuring another on Wednesday.
SD/