A bomb tore through a bus carrying government employees and other civilians in northwestern Pakistan on Friday, killing 18 people in an attack that served as a reminder of the continued militant threat despite a significant drop in violence over the past year, officials said.

The bus was near the city of Peshawar when the bomb planted inside it exploded, almost completely destroying the back half of the colorfully decorated vehicle. The dead included six women, said senior police officer Tahir Ayub Khan. Another 35 people were wounded in the explosion, he said.

Peshawar is located near Pakistan's semiautonomous tribal region, the main sanctuary for Taliban militants and their allies in the country. The city has suffered scores of bomb attacks over the past five years, but violence has fallen in recent months. The drop is partly due to Pakistani military operations against the Taliban in various parts of the tribal region.

Residents frantically shuttled bloodied victims from the bombing to the hospital in taxis, trucks and other private vehicles in the aftermath of the attack, local TV footage showed. Officials wheeled one woman into the hospital on a stretcher. She was covered by a blanket, and her clothes were soaked with blood.

No group claimed responsibility for the attack, but the Pakistani Taliban have carried out hundreds of similar bombings across the country. The group is waging a bloody insurgency seeking to overthrow the government, partly because of its alliance with the United States. The Pakistani military has fought back but has had trouble clearing areas of the tribal region of militants, and they continue to strike back.