The vehicle was almost completely destroyed
At least 13 people have been killed and 10 wounded in a bomb attack on a Pakistani air force bus near the north-western city of Peshawar, police say.
The bomb went off as the bus drove over a bridge near Badaber, an air force base on the outskirts of the city.
Civilians were reported to be among passengers killed or injured. The bus was blown to pieces.
It is the first such attack in weeks and comes as Pakistani troops battle militants in parts of the north-west.
Pro-Taleban fighters operating along the north-west frontier with Afghanistan said they were behind the bombing.
'Crying for help'
The police chief of North West Frontier Province, Malik Naveed Khan, said the bomb appeared to have been remotely detonated.
"Thirteen dead bodies... have now been brought here," the AFP news agency quoted Khan Abbas, a police official at Peshawar's Lady Reading Hospital, as saying.
Another police officer at the hospital said four air force officials and a young girl were among the dead, the agency reported.
An eyewitness said the explosion tossed the vehicle into air, and it caught fire.
"I saw the men on fire inside the vehicle, they were crying for help," he said.
"People rushed to the vehicle and started pulling out the dead and injured. The police arrived at the scene after an hour."
Reports said the explosion left a huge crater. The bus was reduced to a tangle of twisted metal and debris.
Taleban spokesman Maulvi Omar said the attack was in response to military operations against insurgents in the Bajaur tribal region near the Afghan border.
The BBC's M Ilyas Khan in Karachi says this is the first direct attack on security forces in several weeks.
Pakistan saw a wave of militant violence last year with dozens of suicide attacks and bomb blasts which killed hundreds of people.
Violence reduced considerably after a new coalition government came to power after elections earlier this year and opened negotiations with the militants.
But clashes have intensified since top Pakistani Taleban leader Baitullah Mehsud suspended talks in June.