Islamic State has claimed responsibility for the suicide bombing at an election rally in southwestern Pakistan, the group's AMAQ news agency said on Friday.
The group provided no further detail or evidence for its claim.
Pakistani officials said at least 70 people were killed in the attack, the deadliest the country has seen in over a year and the third incident of election-related violence this week.
Balochistan Awami Party (BAP) candidate Siraj Raisani was killed along with 70 people, while 120 were injured in the blast in Mastung district.
Raisani, a candidate of the recently-formed BAP, is the younger brother of former Balochistan Chief Minister Aslam Raisani.
Balochistan security forces told the media that Siraj was attacked during a corner meeting organised for the promotion of his candidature. Siraj`s death was confirmed by his brother Lashkari Raisani.
Balochistan`s Civil Defence Director Aslam Tareen said 8 to 10 kg of explosives and ball bearings were used in the attack.
Civil Hospital spokesperson Waseem Baig said the hospital received 53 bodies and 73 wounded. At least 20 of those injured were in critical condition.
The Mastung bombing was the latest, and deadliest, of a string of attacks targeting politically exposed persons ahead of the July 25 election.
Earlier on Friday, a blast targeted former Khyber-Pakhtunkhwa Chief Minister Akram Khan Durrani`s convoy in Bannu. While Durrani remained safe, four people were killed and 32 others injured in the attack.
The Election Commission of Pakistan has postponed polling for the constituency from where Siraj was contesting.
Earlier this week, a suicide blast had killed Awami National Party leader Haroon Bilour and 19 others in Peshawar.
The attack was owned up by the Tehreek-e-Taliban Pakistan.