- The TTP Jamaat ul Ahrar, a faction of the Pakistani Taliban, claim responsibility
- The group has vowed more attacks until Sharia law is fully implemented in Pakistan
The explosion took place at the city's National Database and Registration Authority offices -- where Pakistanis get ID cards and passports.
Several other people were injured in the attack, said Saad Wazir of the Mardan police.
Police believe a suicide bomber drove his motorcycle into the office building.
Shortly afterward, a faction of the Pakistani Taliban -- the Tehreek e Taliban Pakistan Jamaat ul Ahrar -- claimed responsibility.
"We attacked the National Database Registration Authority office because it plays an essential role in this war," said a statement signed by the group's spokesman, Ehsanullah Ehsan.
"Any Pakistani institution that is involved in this war will continue to be a target for us going forward."
The Pakistani Taliban, known as the TTP, share the same religious extremist ideology as their Afghan namesake but are a distinct group.
The TTP have been fighting to overthrow Pakistan's government via a terrorist campaign, according to the U.S. State Department.
In October, the TTP Jamaat ul Ahrar claimed responsibility for the bombing of a political office
for the country's ruling party, the Pakistan Muslim League Nawaz.
Shortly after that attack, Ehsan vowed the attacks would continue until Sharia law was fully implemented in Pakistan.