Bomb in southern Pakistan kills 2 as Pakistanis vote in historic election

Supporters of Pakistan Tehreek-e-Insaf or Moment for Justice party attend an election campaign rally in Islamabad, Pakistan, Thursday, May 9, 2013. Pakistan is scheduled to hold parliamentary elections on May 11, the first transition between democratically elected governments in a country that has experienced three military coups and constant political instability since its creation in 1947. The parliament's ability to complete its five-year term has been hailed as a significant achievement. (AP Photo/Anjum Naveed) (The Associated Press)

A Pakistani army soldier, guards election material provided to polling agents for tomorrow's elections, in Islamabad, Pakistan, Friday, May 10, 2013. An especially violent spate of killings, kidnappings and bombings marred the run-up to Pakistan's nationwide election, capped Thursday by the abduction of the son of a former prime minister as he was rallying supporters on the last day of campaigning before the historic vote. (AP Photo/B.K. Bangash) (The Associated Press)

A Pakistani girl runs past a car decorated with an election banner showing Mohammed Abdullah, a candidate of a pro-Taliban religious group Jamiat-e-Ulema Islam (JUI-F) in a poor neighborhood on the outskirts of Islamabad, Pakistan, Friday, May 10, 2013. An especially violent spate of killings, kidnappings and bombings marred the run-up to Pakistan's nationwide election, capped Thursday by the abduction of the son of a former prime minister as he was rallying supporters on the last day of campaigning before the historic vote. (AP Photo/Muhammed Muheisen) (The Associated Press)

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.