"Eight people have been killed and 20 injured in the blast," Syed Mohsin Shah, the top administrator of Dera Ismail Khan city, told AFP.
"The bomb was planted in a cycle-rickshaw and it was rush hour in the bazaar at the time of blast," he added.
Ghulam Jailani, a police official in Dera Ismail Khan, said the blast was detonated by remote-control, while officials said dozens were wounded.
"We have received eight dead bodies and 27 injured, five of them are very serious," said Mohammad Ashiq Saleem, a senior doctor in the main government hospital in the town.
Pakistan has been hit by a string of deadly bomb blasts in recent weeks, many of them claimed by the Taliban, who say they are exacting revenge for a punishing military offensive against them across swathes of the northwest.
Security forces launched their campaign in three northwest districts around the Swat valley on April 26 after Taliban fighters advanced towards Islamabad.
Operations recently expanded to Bannu district -- just north of Dera Ismail Khan -- while fighter jets have also bombed militant targets in the nearby semi-autonomous tribal area of South Waziristan.
"In my opinion the blast is a follow-up to the Swat and Waziristan operations," said Mohammad Iqbal Khan, chief of the district police.
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