The officials say 15 people also were wounded in the blasts Friday in Miran Shah, the main town in Pakistan's North Waziristan tribal area. The officials spoke on condition of anonymity because they were not authorized to talk to the media.
Militants have killed at least 130 people in attacks on candidates and party workers since the beginning of April in an attempt to hamper the vote.
It was unclear exactly which candidates were targeted in the latest attack since several have offices in the block where the explosions occurred.
No one has claimed responsibility for the attack, but suspicion will likely fall on the Pakistani Taliban.