Ousted Pakistani Prime Minister Nawaz Sharif and his daughter Maryam were arrested on Friday after flying back to the country to face lengthy prison sentences, in a high-stakes gamble to galvanize their beleaguered party ahead of a July 25 election.
Sharif is expected to appeal his conviction and seek bail.
Sharif has been banned from participating in politics, and his brother Shahbaz Sharif now heads his Pakistan Muslim League and is campaigning for re-election on July 25.
A senior provincial government official also confirmed the figure, adding that 150 others were injured in the attack.
Last month a drone strike killed the leader of the Pakistani Taliban, Maulana Fazlullah, in neighboring Afghanistan in what the Pakistani army called a "positive development" that also sparked fears of reprisals.
During his term in office, Sharif had criticized the military's involvement in civilian affairs and its efforts in fighting extremists.
Pakistani and worldwide rights groups have accused the military of seeking to maintain its influence in Pakistani politics by keeping Sharif out of power. This was the first major incident of violence ahead of the elections in Pakistan. The military denied the accusations saying their assistance in carrying out the elections was requested by Pakistan's Election Commission.
Earlier in the day, a bomb blast killed four people in the northern town of Bannu when it struck the campaign convoy of Akram Khan Durrani, an ally of Sharif's party from the religious Muttahida Majlis-e-Amal party (MMA).
Police had earlier said that the attack targeted Raisani's convoy but later changed their statement as video footage of a large tent showing damage from the blast was circulated.
Durrani is running in the July 25 vote against popular former lawmaker Imran Khan.
Raisani is the second electoral candidate to be killed in pre-election violence this week. Candidate Akram Khan Durrani had just finished his speech when the bomb exploded.
Durrani came under attack in 2015 as well. On Monday, a suicide bomber killed Awami National Party (ANP) leader and candidate in the general elections, Haroon Bilour and 19 others after striking at a corner election meeting in Peshawar city.
"There seems to be a conspiracy to sabotage the 25 July elections but the people of Pakistan will not allow any design meant to target these historic elections to succeed", he tweeted.
"What credibility will these elections have when the government is taking such a drastic action against our people and this crackdown is taking place all over the country?" he told Reuters at the airport in Abu Dhabi as he waited for a connecting flight to Lahore.