Officials in northwestern Pakistan say a bomb blast has ripped through a bus, killing at least 19 people, including six women.

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

The bus was carrying government employees and other passengers and was traveling between Peshawar and the nearby town of Charsadda.

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.

On Thursday, U.S. Defense Secretary Leon Panetta urged Pakistan to take action against militant safe havens, saying the United States is “reaching the limit” of its patience. He made the comments during a visit to Afghanistan.

Friday's blast in Peshawar comes a day after at least 14 people were killed in a bomb attack in Quetta, the capital of Pakistan's southwestern province of Baluchistan.

Police say a bomb planted on a bicycle exploded outside an Islamic seminary Thursday as people gathered to attend a degree ceremony. At least 30 people were wounded in the blast.

Baluchistan has seen militant violence and sectarian attacks and is also home to Baluch separatists waging a low-level insurgency.