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 an Islamist assassin last week.

The bomber, who 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.

"Condition of four to five more injured was critical and doctors are struggling to save their lives," Hasan told AFP.

Fayaz Khan, a senior police official confirmed the new death toll and told AFP that most of the dead have been buried.

School teacher Murid Khan, who was in the complex for a land dispute hearing, said he was getting documents photocopied when he heard gunshots.

"I looked back and there was a huge explosion," he said, adding the blast threw him over the photocopier.

"I heard screams and saw black clouds of smoke, then I fell unconscious" after being hit by two pieces of shrapnel, he said.

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 Islamists after he gunned down the liberal governor of Punjab in 2011 over a call to reform the country's blasphemy law.

Qadri was hanged on February 29 in what analysts described as a key moment in Pakistan's long fight against militancy, saying it demonstrated the government's resolve to uphold the rule of law rather than allow extremism to flourish.

His funeral brought up to 100,000 people on to the streets, hailing him as a hero.

But Peshawar-based senior analyst and retired brigadier Saad Khan said using the name of Qadri was just a cover.

"The main purpose of militant groups is to spread terror and to give a message that they are still alive," he said.

"These groups need covers and using the name of Mumtaz Qadri is just an excuse."

- 'Un-Islamic laws' -

Monday's blast also targeted the court complex because Pakistan's judiciary was strengthening "un-Islamic laws", Ehsanullah Ehsan, a spokesman for the Taliban, told AFP.

Local TV channels showed footage of victims being rushed to hospitals soon after the blast.

Authorities said six women, two children and two policemen were among the dead. Senior regional police official Saeed Wazir praised the bravery of officers who "sacrificed their lives".

There were around 300 people in the complex at the time, another police official said.

Local bar association president Shair Qadir said they had requested security after receiving threats of an attack, but no action was taken in what he termed a police failure.

Shabqadar is near the Mohmand tribal district, one of seven semi-autonomous regions bordering Afghanistan where militants from Al-Qaeda and the Taliban had established bases in the past.

Islamabad launched a military offensive in the tribal areas in 2014 that has reportedly killed thousands of militants and pushed the rest over the border to Afghanistan, resulting in improved security inside Pakistan.

However, insurgents associated with the Pakistani Taliban occasionally carry out attacks from bases inside Afghanistan.

Shabqadar is some 30 kilometres (18 miles) west of Charsadda, where extremists attacked a university on January 20 in a rampage that left 21 dead.
Source :AFP