A bomb attack on a Shiite Muslim procession killed five mourners and wounded more than 80 in Dera Ismail Khan on Sunday as Shiites marked their holiest day Ashura, officials said.
"Five people were killed and 83 injured in the bomb blast," Shafeerulla Khan, a senior government official in regional capital Peshawar told AFP.
Khan said preliminary investigations indicated the device was planted inside a shop but police were probing whether a suicide bomber was involved.
A spokesman for the Pakistani Taliban soon claimed responsibility for the bombing and threatened more attacks.
"It was a suicide attack and we claim responsibility for it," Ehsanullah Ehsan told AFP by telephone from an undisclosed location.
He repeated his threat made Saturday that the Taliban had dispatched more suicide bombers across the country for attacks against the Shia community.
The Pakistani Taliban had also claimed a suicide attack that killed 23 people Thursday at a Shiite procession in the garrison city of Rawalpindi.
But Nazir Khan, a police official in Dera Ismail Khan, insisted Sunday's blast was from a bomb planted inside a shop. "It was a remote-controlled bomb and exploded as a procession reached here," he said.
Police official Anwar Khan Akbar confirmed the new death toll and said the target of the attack was the Ashura procession.
Khalid Aziz, a doctor in the city's main hospital, told a private TV channel some of the injured were in critical condition.
Government has deployed tens of thousands of police and paramilitary forces to try to avert sectarian clashes or attacks on Ashura processions.
Authorities have ordered heightened security, with services for mobile phones -- which are often used to trigger bombs -- suspended in major cities.
Interior Minister Rehman Malik has sought a report from the IGP and directed for an immediate inquiry into the incident.