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.
"My brother Siraj Raisani has been martyred", said Haji Lashkari Raisani, another brother who is also contesting a national assembly seat from Balochistan.
The first bomb that killed four people exploded in northwest Pakistan near the election rally of a senior politician from an Islamist party who is running for parliament from the northwestern town of Bannu.
It came as Pakistan's caretaker government launched a crackdown on political gatherings with Sharif, who was ousted by the Supreme Court previous year and convicted in absentia of corruption a week ago, arriving in the country to rally his party ahead of the general elections.
Disgraced former Prime Minister Nawaz Sharif will be whisked away by helicopter to the federal capital of Islamabad when he returns Friday to Pakistan from London to face a 10-year prison sentence on corruption charges, anti-corruption officials said.
Raisani is the brother of the former Baluchistan chief minister, Aslam Raisani. Unidentified officials said the blast targeted his corner meeting.
Baluchistan caretaker Health Minister Faiz Kakar told Reuters that the death toll in the attack had risen to 85 people, with over 150 wounded.
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The attack came hours after a bomb hit a rally of Akram Khan Durrani of Mutahida Majlis Amal (MMA), an alliance of religious party, including Jamiat Ulema-e-Islam-Fazal (JUI-F) and Jamaat-e-Islami, in Bannu area of Khyber-Pakhtunkhwa province.
No group has claimed responsibility for the two attacks so far.
Pakistan Tehreek-e-Insaf Chief Imran Khan took Twitter to condemn the attack.
The country's media regulator warned local news channels to abstain from airing statements "by political leadership containing defamatory and derogatory content targeting various state institutions specifically judiciary and armed forces", the regulator said in a statement. Thousands flocked to his funeral the next day.
His father, senior ANP leader Bashir Bilour, was killed in a suicide bombing in late 2012, in the run-up to Pakistan's last election.
Following the series of attacks, activists called for Pakistani authorities to remain vigilant to protect candidates during the final days of the campaign season.
But security across the country has dramatically improved since government and military operations cleared large swathes of territory near the Afghan border in recent years.