Raisani also died in the blast, while 35 others were injured, reported The Express Tribune.
The attack took place in Darengarh area in Mastung.
Raisani's convoy was attacked after the BAP party workers attended a corner meeting for provincial assembly seat PB-35. Raisani is the younger brother of former Balochistan chief minister Mohammad Aslam Khan Raisani.
Deputy Commissioner (DC) Mastung Qaim Lashari was quoted by Geo TV saying that the injured were shifted to nearby hospitals and are investigating. Additional medical staff have been deputed in all Quetta hospitals, as an emergency has been declared.
Earlier in the day, at least four people were killed and dozens of others were injured in an explosion in Bannu in Pakistan's Khyber Pakhtunkhwa province.
The bomb exploded near the rally of Jamiat-e-Ulema Islam (F)'s Akram Khan Durrani, who is contesting election against Pakistan Tehreek-i-Insaf (PTI) chairman Imran Khan. Durrani escaped the attack unhurt, Geo News quoted Regional Police Officer (RPO) Bannu Karim Khan, as saying.
The RPO also told Geo TV that the explosion went off 50-metres away from Durrani's rally, where he was canvassing for the July 25 general elections.
On Monday, Awami National Party (ANP) candidate from Peshawar Haroon Bilour, and 19 others were killed in a powerful suicide blast in Peshawar. The attack was claimed by the Tehreek-i-Taliban Pakistan.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)