Hundreds of people were gathering inside the preaching center for Friday prayers when the blast went off.
Initial reports said that it was a gas cylinder blast, but local officials later confirmed it was a blast of terrorist nature.
The bomb was planted in the basement of the preaching center, they said.
At least 22 people were killed and 65 others injured in the blast, said local media, adding that many of the wounded people died later at hospital.
While the people in the country have not recovered from the shock of the two blasts that hit Quetta and Swat, there came in another report saying a more deadly twin blast hit Quetta again.
The two blasts happened just within a few minutes, said sources of Xinhua in the city.
The first one hit a snooker club located on the Alamdar Road of the city at about 8:50 p.m. local time.
It was a suicide blast, said bomb disposal squad officers, adding that an estimated six to seven kg of explosives were used by the suicide bomber.
As police, rescuers and media persons rushed to the blast site, another bomb fixed in a vehicle parked nearby the site went off, causing a large number of casualties among the people gathering on the first blast site.
A web user recently posted a photo of a twisted building in the suburb of Beijing, calling it "Tower of Large Intestine".