Describing the latest attack, James Bays, Al Jazeera's correspondent in Islamabad, the capital, said: "We understand it was not a suicide bomb. It was planted in a rickshaw in a very busy market area near one of the main bus stops in Dera Ismail Khan.
"It seems to have been timed to kill as many people as possible.
"Sunday is a holiday here. Many people were shopping at the time of the explosion. We hear that three shops in the market have been completely destroyed."
Dera Ismail Khan is not far from North and South Waziristan, in the Federally Administered Tribal Areas, where the Pakistani military has been using air raids and artillery to bombard a stronghold of Baitullah Mehsud, a senior leader of the Pakistani Taliban.
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 taking revenge for the military offensive against them across the northwest.
The army launched its campaign in three northwest districts around the Swat valley on April 26 after Taliban fighters advanced towards Islamabad.
The military recently expanded its operations to Bannu district, just north of
Dera Ismail Khan.
In a separate incident on Sunday, a suspected US missile strike killed five people in South Waziristan.
The US, alarmed by the deteriorating security in Afghanistan, has been using drone aircraft to attack Taliban and al-Qaeda fighters in northwestern Pakistani strongholds.
The drone strike on Sunday, the first since May 16, was in Laddah, in South Waziristan, about 60km north of the region's main town of Wana.
A government official in the region confirmed the attack, saying drones had been flying over South Waziristan since early morning. The identity of those killed was not known.