Local police officials said that the blast took place at about 6:10 p.m. local time in Meetha Chowk market of Pashtoon Abad area in Quetta, provincial capital of the country's southwestern province of Balochistan.
The blast killed one person on spot and injured over 20 others including at least eight children, police said.
Police, paramilitary forces and rescue teams rushed to site and shifted the body and the injured to the hospital where five of the injured including one child were reportedly in critical condition.
According to bomb disposal squad, over two kilograms of explosives were used in the bomb that was planted near an ice- cream shop and detonated through a time device.
People were shopping when the bomb exploded with a big bang that destroyed eight nearby shops and half a dozen of fruit pushcarts beside smashing window panes of nearby buildings.
Police has launched an investigation into the incident besides launching a search operation in the nearby areas to arrest the culprits.
No group claimed responsibility for the attack yet.
In another incident, some unknown people hurled a hand grenade at a house located on the Kohat road of northwestern provincial capital of Peshawar that injured three people.