The attack was the second to strike the city in Khyber-Pakhtunkhwa in as many days.
The bomb, planted in a shop in Chogla area of Dera Ismail Khan, was triggered by remote-control as a procession was passing by.
A security personnel was among the six persons killed in the attack, Khyber-Pakhtunkhwa Information Minister Mian Iftikhar Hussain said.
Four security personnel, women and children were among the injured.
Several of the wounded were in a critical condition.
Yesterday, eight persons were killed and about 20 injured when another Shia procession was targeted with a roadside bomb in Dera Ismail Khan.
The banned Tehrik-e-Taliban Pakistan claimed responsibility for both bombings in the city as well as a suicide attack on a Shia procession in Rawalpindi that killed 23 people and injured over 60 on Wednesday.
Authorities called in army soldiers to patrol the streets of Dera Ismail Khan after the attacks.
The bombings caused widespread panic in the city.
Tehrik-e-Taliban Pakistan spokesman Ihsanullah Ihsan told the media that his organisation had carried out today's attack.
He claimed a suicide bomber was in the procession in Dera Ismail Khan though officials insisted the attack was carried out with a bomb.
Ihsan said the Taliban would succeed in striking their targets despite all security arrangements made by Interior Minister Rehman Malik.
Provincial Information Minister Hussain said the Taliban had apparently planned the attack in Dera Ismail Khan well in advance as authorities had closed all shops and markets and suspended mobile phone services in the city.
The bomb was planted in a closed shop on the route of the Shia procession and triggered by remote control, he said.
The elements targeting Shia prayer halls and processions during the Islamic month of Muharram are enemies of the country, he said.
Muharram is a holy month and those violating its sanctity have nothing to do with religion, he added.
Pakistani authorities have put in place extensive security arrangements to prevent terror attacks on thousands of processions organised across the country during Ashura, the 10th day of Muharram that is observed today.
Mobile phone services have been suspended in nearly 50 towns and cities, including Karachi, Lahore and parts of Islamabad, with Interior Minister Malik saying cellular phones were used to trigger bombs in "90 per cent" of recent attacks.
Tens of thousands of police and paramilitary personnel have been mobilised to guard the Shia processions and the army has been called out or put on stand-by in sensitive areas.
Officials have also appealed to Shia and Sunni scholars and clerics to help maintain calm and not to get provoked by any incident.