ISLAMABAD, Pakistan — An explosion ripped through a police bus on the edge of Peshawar on Friday, killing at least 19 people and wounding dozens in the deadliest attack in months in the northwestern city.

The provincial information minister, Mian Iftikhar Hussain, said the bus was traveling to Charsadda, carrying private passengers and employees of the Khyber Pakhtunkwa government, when a bomb went off.

“The bomb was planted under the bus,” Mr. Hussain told reporters, adding that he was not sure how many of the passengers worked for the government. A senior police official said that six women and one child were among the dead.

Television footage from the scene showed the twisted wreckage of a bus under a line of trees, and the bloodstained belongings of its passengers scattered across the road.