At least 128 people, including Balochistan Awami Party leader Siraj Raisani, were killed and almost 200 others injured in a suicide attack in Balochistan on Friday.
"Initially the death toll was not high but many critically injured persons including Siraj Raisani passed away in hospitals", Balochistan's caretaker health minister Faiz Kakar said. Another senior official, Qaim Lashari, also confirmed it was a suicide blast.
The ultraviolent Islamic State or Daish terror outfit claimed responsibility for the deadly attack in a short statement.
The suicide bombing was the second election-related violence to take place on Friday.
Speaking to reporters after the attack, JUI-F leader Akram Khan Durrani said the blast took place near the tire of his jeep when he was passing through Haved Bazaar after addressing an election rally.
"Mir Siraj Raisani succumbed to wounds while he was being shifted to Quetta", he added.
Mr Raisani was the brother of the former Baluchistan chief minister, Aslam Raisani.
The attack was the deadliest yet ahead of the July 25 parliamentary election and it came despite assurance from the military that it would take all possible measures to ensure a peaceful environment for the vote.
Earlier in the day, at least four people were killed and 39 injured after a bomb hidden inside a motorcycle detonated as a Pakistani politician's convoy passed by.
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Days earlier a bomb claimed by the Pakistani Taleban targeted a rally by the Awami National Party (ANP) in the city of Peshawar on Tuesday.
He also used the opportunity to again criticise Pakistan's powerful military, which has ruled the country directly or indirectly for most of its 71-year history, saying Pakistan now has a "state above the state".
The Pakistani Taliban claimed responsibility for the attack. Other local authorities confirmed the attack.
Durrani, the Muttahida Majlis-e-Amal (MMA) candidate, survived the attack.
Local ANP leader Haroon Bilour was among those killed.
Director General Inter Services Public Relations (ISPR) Major General Asif Ghafoor in a tweet condemned the gruesome attacks in Mastung and went on to declare that, "Pakistan has lost a highly devoted & capable politician,". But analysts have long warned that the country has not tackled the root causes of extremism.
The election will pit the PML-N against its main rival, the Pakistan Tehreek-e-Insaf, a party led by cricket star-turned-politician Imran Khan.
Expressing concerns over such attacks during election campaigns, he called for serious investigations in these attacks.