Hospital officials confirmed the toll.
Zeb said there were 18 bodies at the Landi Kotal hospital while seven of the injured died while being taken for treatment at Hayat Medical Complex (HMC) in Peshawar, the main town in northwestern Khyber Pakhtunkhwa province.
The dead included three children aged nine, 10 and 12, Zeb said.
Tauheed Zulfikar, a doctor at HMC, said, "We have received seven bodies."
There was no immediate claim of responsibility but Islamist militants have carried out several attacks in the area.
Since July 2007, a Taliban-led insurgency concentrated in the northwest has fought Pakistan's US-allied government.
Arshad Khan, a local administration official, said the blast appeared to be aimed at members of the pro-government Zakha Khel tribe, who oppose a local warlord, Mangal Bagh.
Bagh's Lashkar e Islam group has links to Islamist militants and criminal gangs.
"The bomb was planted in a pick-up truck parked near the bus stand," Khan said.
In the last five years, attacks blamed on Islamist bombers have killed more than 5,000 people in Pakistan according to an AFP tally.
US officials consider the country's semi-autonomous tribal belt a safe haven for al Qaeda and insurgents fighting both in Pakistan and across the border in Afghanistan.
Copyright 2012 AFP. All rights reserved.