A suicide bomber set off a powerful explosion that killed at least 20 people and wounded more than 50 in northwestern Pakistan on Tuesday, police and hospital sources said.
The blast targeted a crowd near the office of the National Database and Registration Authority in the city of Mardan, where a large number of people had lined up to obtain national identity cards.
A breakaway faction of the Pakistani Taliban called Jamaat-ul-Ahrar claimed responsibility for the attack. A spokesman for the militant group told the Associated Press the bombing was "to punish NADRA" because it provides support to Pakistani security forces.
Saeed Wazir, a senior police officer in Mardan, 30 miles northwest of the city of Peshawar, told reporters that body parts of the suicide bomber had been collected from the site. He said a security guard attempted to stop the attack, but the bomber rammed his motorbike into the gate of the agency's building.
Witnesses said they saw a burning motorbike lying at the gate.
Wazir said large numbers of applicants were waiting for their turn to receive identity cards. Under Pakistani law, every citizen above the age of 18 must carry one.
Bilal Ahmad Faizi, spokesman for state rescue agency Rescue 1122, said 21 bodies had been counted at the city's main hospital while 56 people were in critical condition.
Officials with the Bomb Disposal Unit said around 20 pounds of explosive material was used in the attack.
This was the second deadliest explosion this month to strike northwestern Pakistan, following several months of relative calm. The Pakistani army has been carrying out a year-and-a-half-long offensive against militant groups in the region.
On Dec. 13 a bomb ripped through a makeshift market in the town of Parachinar near the Afghan border, killing 26 people and wounding 30. A militant group took responsibility for that attack, saying it was aimed at residents of the majority Shiite Muslim town.
Ali is a special correspondent.