The bomb was detonated during prayers at the mosque, Dawn News reported.
"One of the attackers wearing a suicide vest entered the mosque and blew himself up in front of the worshipers," said Superintendent of Police Rural Shafiullah Khan.
Khan said three attackers tried to enter the mosque and two were prevented from entering by guards. The third managed to get in and was shot at by guards before he detonated the vest.
Witnesses told the BBC there were about 200 people in the mosque at the time of the bombing.
In another Mosque attack, unidentified gunmen shot and killed a provincial Parliament member and his son in Karachi, the BBC reported. The two were exiting the mosque when they were shot.