Dawn.com, Peshawar :Twenty-one people were killed and at least 56 injured when a powerful blast occurred near the National Database and Registration Authority (Nadra) office on Nisatta Road in Mardan, Khyber Pakhtunkhwa, on Tuesday.The attack was claimed by Tehreek-i-Taliban Pakistan (TTP) splinter group Jamaatul Ahrar, which was also behind last year’s deadly blast at Wagah Border. Rescue 1122 spokesman Bilal Ahmed Faizi said officials rushed to the site of the Mardan attack, adding that at least 21 people were killed in the blast.The blast took place at a time when the office was crowded with people lining up to make applications for National Identity Cards (NIC). Map showing the location of the office. Deputy Inspector General Mardan Division Saeed Wazir told DawnNews the blast was a “suicide attack carried out by a bomber”. The DIG added that a security guard posted at the office stopped the bomber at the gate, after which he detonated his suicide vest. The suicide attacker was on a motorbike and rammed it into the gate after being denied entry, he said. Conflicting reports suggest that explosives may have been planted on a motorcycle parked near the Nadra office. Officials of the Bomb Disposal Unit that reached the scene of the explosion said around 8 to 10 kg of explosive material was used in the attack.According to initial reports, the powerful blast took place near the gate of the office and damaged doors and windows in the building. At least 40 people are said to be injured, with some in serious condition.Human body remains were strewn across the blast site. The area was cordoned off as rescue and security sources rushed to the site. The injured were shifted to Mardan Medical Complex, while an emergency was declared at all medical facilities in the area. The office is located on the link road that connects Charsadda to Mardan. Mardan is situated in Khyber Pakhtunkhwa province, which has seen several terrorist attacks over the past several years – many of them targeting security officials.Earlier in December, a search and strike operation was launched in Mardan, resulting in the arrest of about 327 suspected persons, including 16 illegally staying Afghan nationals, and persons involved in various crimes.Mardan District Police Officer Faisal Shehzad, talking to media persons, had disclosed that the search and strike operation was carried out in Par Hoti, Bashkhali, Gujraat, Iranabad, Chora, Bhaijan, Surakh Dheray, Katakhet, Barikab, Galyara and localities adjoining the city.He said they had also established checkposts jointly manned by police and army personnel at different points of the district and around 500 vehicles were searched with the purpose to take suspected passengers into custody if there were any inside those vehicles.