The bomber wearing burqa entered the Imambargah Kazmia Chilgiri, used for religious services by the minority community, at the time of evening prayer and exploded an explosive-laden vest.
Balochistan Home Minister Sarfaraz Bugti said that the explosion occurred moments before a religious gathering was about to begin.
Bugti said that six children between 10 and 12 years old were among the dead. About 12 people were also injured in the blast.
No one claimed responsibility for the attack.
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Interior Minister Chaudhry Nisar Ali Khan condemned the blast.
It was the first major attack that targeted the minority Shia Muslims in the holy month of Muharram when they organise special prayers and take out processions.
Security has been beefed up across Pakistan for Ashura, the tenth day of Muharram to commemorate the death of Hussain, the grandson of the prophet Muhammad.
Police have set up extra checkpoints and imposed restrictions on movement in some areas.