Sahibzada Mohammad Anis, commissioner for Peshawar, said it appeared that a bomb had been planted on the bus.
In addition to the fatalities, hospital officials said, at least 42 people were injured.
Tahir Ali, a 39-year-old farmer, said he ran to the scene after hearing the explosion and found the rear of the bus nearly sheared off. “I saw destroyed seats, bloodstains and pieces all around,” he said. “There were dead bodies and injured people on the bus crying for help.”
Shabir Khan, 31, who witnessed the explosion, said about 100 people were on the bus at the time.
By nightfall, there was still no claim of responsibility. A spokesman for the Pakistani Taliban said he was not aware of any of the group’s members being involved. But the attack appeared likely to become another flash point in the debate in Pakistan about how to combat a growing terrorism threat.
Although Islamabad and other central areas remain relatively secure, militants thrive in western areas near Pakistan’s border with Afghanistan. But Karachi, the country’s largest city, main seaport and economic hub, is also combating a string of killings and kidnappings by militants or criminal gangs. And officials worry about a growing threat from Islamist extremists in rural areas outside the eastern city of Lahore.
For years, Peshawar has endured some of the worst acts of violence.
In an attack that stunned the nation, two suicide bombers detonated powerful explosives outside a historic Protestant church after services ended Sunday. The attack, which killed 85 worshipers and injured more than 120, is believed to have been the deadliest attack on Christians in Pakistan’s 66-year history.
The Taliban leadership in Pakistan distanced itself from the church bombing. But a Taliban-linked Sunni extremist group, Jundallah, said it had carried it out to protest U.S. drone strikes on Pakistani soil.
As a result of that attack, Prime Minister Nawaz Sharif is reconsidering plans to hold peace talks with the Taliban.
But other political leaders, including former cricket star Imran Khan, who leads the political party that heads Khyber Pakhtunkhwa’s provincial government, is pushing for the talks to continue.
“Let there be a dialogue,” Khan told reporters Wednesday as he visited the victims of the church bombing in the hospital. “War is not a solution to any problem.”
Craig reported from Islamabad.