Pakistani police say a powerful bomb has exploded at an open-air market in the southwestern city of Quetta, killing at least seven people and wounding 20 others.

Police chief Abdur Razzaq Cheema says Friday's bombing took place near a residential area where minority Shiite Muslims live.

He says authorities are transporting the dead and wounded to hospitals.

No group has immediately claimed responsibility for the attack but outlawed Sunni extremist groups have claimed similar attacks in the past. Sunni extremists view Shiites as apostates deserving of death.

Quetta is the capital of Baluchistan province, which also is the scene of a low-level insurgency by separatists demanding more autonomy and a greater share in the region's natural resources such as gas and oil.