At least 31 people, including three policeman and two children, were martyred in a suspected suicide attack outside a polling station near Eastern Bypass in Quetta on Wednesday, hospital sources said.
Thirty others were injured in the attack.
Rescue sources said the explosion occurred near a police vehicle on routine patrolling.
A police spokesperson said, the suicide bomber wanted to enter the polling station.
"The suicide bomber blew himself up when police and FC personnel stopped him from entering the station," the police spokesperson said.
The bomb disposal squad has also reached the site of the attack after reports that an unexploded grenade has been discovered.
DIG Abdul Razzak Cheema said the injured have been shifted to Sandeman Provincial Hospital. A state of emergency has been declared at the hospital.
The border crossing between Pakistan and Afghanistan in Chaman, Balochistan was closed by the government on Tuesday for two days in the wake of the general election.
Polling across the country for the 11th General Election began at 8am.