Watch | Suicide bomb blast kills 21 in northwestern Pakistan

At least 21 people were killed and dozens sustained injuries when a Taliban suicide bomber blew himself up at the main gate a government office in the northwest Pakistan town of Mardan, officials said.The blast highlights the Pakistani Taliban's continued ability to carry out attacks despite a major military offensive against its headquarters that analysts say has reduced the group's capacity.The explosion ripped through the front entrance of a regional branch of the National Database and Registration Authority (NADRA), which is responsible for issuing ID cards.