Officials in northwestern Pakistan say a bomb blast has ripped through a bus, killing at least 18 people, including six women.

Authorities say some 35 people were wounded in the attack Friday in Peshawar, near Pakistan's semi-autonomous tribal region, along the Afghan border.

No one has claimed responsibility for the attack, but the Pakistani Taliban have carried out hundreds of similar bombings across the country.

The Pakistani Taliban, the Afghan Taliban, al-Qaida and affiliated militant groups are entrenched in the tribal regions and take advantage of the porous border to launch attacks against NATO and Afghan forces in Afghanistan.