Peshawar, Dec 29 (PTI): At least 22 people were killed and 40 injured today when a motorcycle-borne Taliban suicide bomber crashed through the gate of a crowded government office in northwest Pakistan and detonated his explosives-laden vest.

The powerful blast happened at the National Database and Registration Authority (Nadra) office, which issues government ID cards, in Mardan town of Khyber-Pakhtunkhwa, damaging doors and windows of the building.

An emergency rescue officer said at least 22 people were killed in the suicide blast at a time the office was crowded.

Human body parts were seen strewn across the blast site.

Deputy Inspector General Mardan Division Saeed Wazir confirmed that it was a "suicide attack."

District police officer Mardan said it was "too early" to determine the nature of the blast.

Officials of the bomb disposal unit at the scene said 8-10 kg of explosives was used in the attack claimed by Tehreek-i- Taliban Pakistan splinter group Jamaatul Ahrar, which was also behind last year's Wagah Border blast, Dawn news reported.

According to reports, a suicide bomber ridding on a motorcycle rammed through the gate after the security guard posted there denied him entry.

The injured, several of them critical, were shifted to Mardan Medical Complex and other hospitals in the city, where a state of emergency has been declared.

The area has been cordoned off as rescue and security officials rushed to the site.

The Nadra office, charged with the establishment of a new registration system for the entire population of Pakistan, most of the time remains crowded.