Bomb blasts also targeted political workers and offices in Peshawar, Quetta and several other places in Balochistan province.
Three persons were killed and 12 others injured when a blast ripped through the market of Miranshah, the main town in North Waziristan tribal region.
The explosive device was attached to a motorcycle and detonated by remote control, security officials said.
The bomb was detonated while a car was passing by the motorcycle. All occupants of the car were killed instantly.
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In the restive Kurram tribal region, three security personnel were killed when militants attack on a check post.
Nine militants were killed in retaliatory action by the security forces, officials said.
In Quetta, the capital of Balochistan, five persons were injured when a grenade was lobbed at an election office of Pakistan Peoples Party leader Umar Gorgaij. Several vehicles were damaged in the attack on Brewery Road.
The injured were taken to a nearby hospital, where doctors said they were out of danger.
Blasts targeted two schools to be used as polling stations at Panjgur in Balochistan.
An explosion also occurred near the house of a BNP-A candidate in Panjgur, though no one was hurt in these attacks.
No group claimed responsibility for any of the attacks.
Political parties have been under attack since the poll date was announced and around 100 people have died in bombings and attacks by militants over the past four weeks.