In southwest Pakistan, police say militants attacked and set fire to three NATO tankers transporting fuel for U.S.-led forces in Afghanistan.
The three tankers were attacked in Baluchistan near the border with Iran and Afghanistan.
These attacks comes just days after Pakistan re-opened the border crossing following an 11-day closure imposed after a cross-border airstrike by NATO forces.
Elsewhere in Pakistan, a suicide car bomber attempted to attack a military checkpoint in the northwestern district of Lakki Marwat and security forces opened fire on him. Three people were wounded in the resulting explosion.
Thirty-one people were killed in election-related violence that broke out Saturday in Pakistan's southern port city of Karachi. Twenty people have been arrested.
The election was being held Sunday to replace provincial lawmaker Raza Haider from the Muttahida Quami Movement (MQM), who was gunned down in August. MQM, which largely represents the Urdu-speaking community, and the rival Awami National Party, representing ethnic Pashtuns, blamed each other for the violence.
Some information for this report was provided by AFP and AP.