A Pakistani police officer says two people were killed when a bomb exploded outside a political office in southern Pakistan on election day.

Shabir Hussain said 20 people were also wounded in the blast Saturday in the port city of Karachi.

The bomb hit the offices of the Awami National Party. It is one of three secular, liberal parties that have been singled out by Taliban militants.

The blast marred a historic day in Pakistan, where voters are coming out in droves to elect a new government.