A bomb exploded on a bus in Pakistan's troubled northwestern city of Peshawar on Saturday, killing at least nine people and wounding seven others, officials said.
"At least nine passengers have been killed and seven injured. Bomb disposal officials told me that it was a timed device," Fazal Wahid, a senior police official informed.
Shafi Ullah Khan, another police official, confirmed the attack which occurred as the bus was passing through the city's Matani suburb.
Sayed Jameel Shah, a spokesman for Peshawar's main Lady Reading Hospital said nine dead bodies and 19 injured, including three women, had been brought to his hospital.
There was no immediate claim of responsibility for the blast, but Peshawar, which is the capital of the Khyber Pakhtunkhwa province, is routinely targeted by the Pakistani Taliban who are waging an insurgency against the state.
An intelligence official in the city said the attack may be a reaction to a fresh military push in the Tirah valley of the Khbyer tribal district, where the army has been fighting Taliban and Lashkar-e-Islam militants.
Military officials said heavy fighting between Pakistani troops and militants has killed 23 soldiers and 110 militants in Khyber this week.
Khyber straddles the NATO supply line into Afghanistan, used by US-led troops to evacuate military equipment ahead of their 2014 withdrawal, and officials say it is key to protecting security in Peshawar for elections next month.
Another senior police official, Imran Shahid said police were investigating the possibility a suicide bomber was involved.
Subhan Ullah, a shopkeeper in the nearby market, who sustained an injury on his left shoulder told AFP from his hospital bed that the bus was moving when the the blast took place.
"The bus was moving at the time of the blast. It stopped for a while in the market and the blast took place some minutes after it took on passengers," he said.
Hours earlier, militants blew up the election office on an independent candidate standing in elections next month, adding to security fears ahead of historic national polls next month.
A recent wave of terror attacks has fuelled concerns that violence will mar general elections on May 11, which will mark the country's first democratic transition of power after a civilian government has served a full term in office.
Pakistan says more than 35,000 people have been killed as a result of terrorism in the country since the 9/11 attacks on the United States.