Hospital officials said on Friday that the toll in that attack had risen to 22.
It was the second election-related violence to occur on Friday. Local Geo TV said Sharif and his daughter were taken to another waiting aircraft to be flown out of Lahore, where more than 10,000 Sharif supporters were gathered to greet him.
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.
In the first incident near the KP town of Bannu, four people were killed and 39 injured when a bomb hidden inside a motorcycle detonated as a politician's convoy passed by on Friday, police said.
During his term in office, Sharif had criticized the military's involvement in civilian affairs and its efforts in fighting extremists.
Their return could shake up an election race marred by accusations Pakistan's powerful military is working behind the scenes to skew the contest in favor of ex-cricket hero Imran Khan, who describes Sharif as a "criminal" who deserves no support.
MASTUNG: More than 100 people including Nawabzada Siraj Raisani, younger brother of former chief minister Balochistan Aslam Raisai and BAP candidate for Balochistan Assembly, have been martyred and about 150 others injured in a suicide blast in Mastung.
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Schnatter remains on the board, and is still the company's largest shareholder with almost 30 percent of the stock. For the first three months of this year, the chain said a key sales figure fell 5.3 per cent in North America.
Initial investigation suggested it was a suicide attack, Lashari added. The army will deploy 350,000 security personnel to polling stations throughout the country on election day. Durrani is standing against cricketer-turned-politician Imran Khan, whose Pakistan Tehreek-e-Insaf party (PTI) is one of the frontrunners in the July 25 vote. He is a candidate of Muttahida Majlis-e-Amal, an election alliance of radical religious groups.
Raisani is the second electoral candidate to be killed in pre-election violence this week.
Durrani's convoy attacked in Bannu.
Caretaker Chief Minister Dost Mohammad Khan condemned the incident and summoned an emergency meeting to discuss the security situation in the aftermath of the attack. In a tweet, he said there seems to be a conspiracy to sabotage the July 25 vote.
On Tuesday, a bomb claimed by the Tehreek-i-Taliban Pakistan (TTP) militant group targeted a rally by the Awami National Party (ANP) in the city of Peshawar.
"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.