The wave of political violence has killed at least 60 people in recent weeks, and many of the attacks have been directed at candidates from secular parties opposed to the Taliban. That has raised concern the violence could benefit hard-line Islamic candidates and others who are more sympathetic to the Taliban because they are able to campaign more freely without fear of being of being attacked.
Pakistani Taliban spokesman Ahsanullah Ahsan claimed responsibility for the three attacks, plus two others against secular parties in the southern port city of Karachi on Saturday that killed four people and wounded over 40.
"We are against all politicians who are going to become part of any secular, democratic government," Ahsan told The Associated Press by telephone from an undisclosed location.
The first bomb on Sunday ripped through the campaign office of Syed Noor Akbar on the outskirts of Kohat city, killing six people and wounding 10, police officer Mujtaba Hussain said.
A second bomb targeted the office of another candidate, Nasir Khan Afridi, in the suburbs of Peshawar city. That attack killed three people and wounded 12, police officer Saifur Rehman said.
The politicians were not in their offices at the time of the blasts. They are both running as independent candidates for parliament to represent constituencies in Pakistan's rugged tribal region along the Afghan border, the main sanctuary for Taliban and Al Qaeda militants in the country.
Many politicians running in the May 11 election from the tribal region have their offices located elsewhere and find it hard to campaign in their constituencies because of the danger. The two who were attacked Sunday are considered to hold relatively progressive views compared to the deeply conservative Islamic beliefs of many in the tribal region.
The third attack occurred in the town of Swabi, where a bomb went off during a small rally held by the Awami National Party, which has been repeatedly targeted by the Taliban. The blast killed two people and wounded five, said police officer Farooq Khan. The two candidates targeted in the attack, Ameer Rehman and Haji Rehman, were not hurt.
The Pakistani Taliban have been waging a bloody insurgency against the government for years that has killed thousands of civilians and security personnel. The group's goal is to oust Pakistan's democratic government and implement a system based on Islamic law.
In mid-March, the Taliban threatened attacks against three secular parties that have earned the militants' ire by supporting military operations against them in the northwest: the Awami National Party, the Muttahida Quami Movement, and the Pakistan People's Party. The Taliban have carried out at least 20 attacks against politicians and campaign workers since then, mostly from these three parties.
The violence has forced the parties to close dozens of campaign offices and has prevented them from holding large political rallies that are normally the hallmark of Pakistani elections. Many of the candidates have had to find ways to campaign from a distance, relying more on social media, advertisements and even short documentaries to rally support.
That has put these candidates at a disadvantage, and many have complained the militant violence amounts to vote rigging.
Candidates from Islamic parties and others who have advocated negotiating peace with the militants rather than fighting them have been able to campaign with much less fear of being attacked.
Former Prime Minister Nawaz Sharif, head of the Pakistan Muslim League-N party, held a rally with several thousand people in the northern town of Murree on Sunday without incident. Many analysts predict Sharif's party will come out on top in the parliamentary election.
The Taliban issued a statement earlier this year requesting that Sharif and the heads of the country's two largest Islamic parties mediate peace negotiations. Sharif declined but said he was a supporter of the talks.
The parties that have been targeted by the Taliban also support peace negotiations with the militants, but only if they lay down their weapons and accept the constitution first – conditions the militant group has rejected.
* Associated Press Writers Riaz Khan and Rasool Dawar in Peshawar contributed to this report.