A bombing at a market in Quetta, capital of Pakistan's restive Baluchistan province, killed at least four people and injured nearly two dozen on Wednesday.
The bomb disposal squad, arriving at the blast site soon after the explosion, said 6-7 kilograms of explosives were planted on a motorcycle that destroyed several vehicles parked outside repair workshops and badly damaged nearby buildings and shops.
The blast was followed by another explosion, which officials believed was caused by a gas cylinder exploding inside one of the vehicles damaged in the first blast.
Witnesses, rushing to the blast site, said they saw the dead and injured lying all over the busy street soon after the blast. Several cars were on fire.
The injured were shifted to nearby hospitals for treatment, where doctors said three were in critical condition.
So far no one has claimed responsibility for the blast.
Islamic militants and separatists have a decades-long history of anti-government rebellion in the province.
Some information in this repot was contributed by Reuters.