Story highlights 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

Karachi, Pakistan (CNN) At least 26 people were killed in a blast Tuesday in the northern Pakistani city of Mardan, police said.

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.

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