A suicide bomber killed 17 people and injured 31 in northwest Pakistan Monday, in an attack which the Taliban described as revenge for the hanging of a Taliban assassin last week.

A suicide bomber killed 17 people and injured 31 in northwest Pakistan Monday, in an attack which the Taliban described as revenge for the hanging of a Taliban assassin last week.

The bomber, whom police said was aged around 20 and had up to six kilograms (13 pounds) of explosives strapped to his chest, attacked as lawyers and litigants were arriving at a court complex during the morning rush hour in the town of Shabqadar.

Senior government official Tariq Hassan said the death toll rose to 17 late Monday as four more of those injured succumbed to their injuries in hospital.

Officials earlier said that 13 people had been killed and 23 wounded after the bomber blew himself up inside the complex.

The Pakistani Taliban's Jamat-ul-Ahrar faction claimed responsibility for the attack, saying it avenged the hanging of Mumtaz Qadri - feted as a hero by terrorists after he gunned down the liberal governor of Punjab in 2011 over a call to reform the country's blasphemy law.