At least 15 people were killed and more than two dozen injured on Wednesday when a bomb hit a bus in north-western Pakistan, police said.
The bomb was planted under a seat with a timer device, police officer Abbas Majid Marwat said.
Most of those killed were government employees on their way to work in Peshawar, around 200 kilometres west of Islamabad, the town's deputy commissioner Riaz Mehsud said.
“It is not possible to provide security to every vehicle in early rush hours when thousands of vehicles are on the roads,” he said.
Around five injured were in critical condition, Geo TV reported.
TV footage showed the bus badly damaged in the explosion near the Sunehri Masjid, or Golden Mosque of Peshawar.
A witness who was on the bus told Geo TV there were no security checks as the bus picked up other passengers along its route from Mardan, about 50 kilometres to the north-east of Peshawar.
No group claimed responsibility.
Pakistan has been battling a Taliban insurgency for more than decade, as rebels frequently target civilians and security officials.
A suicide bomb hit a court in Charsadda near Peshawar last week, killing around 17 people.