Two blasts in Parachinar on Friday killed at least 25 people, a government official told media, the second deadly bomb attack in the country of the day.
The first blast came during rush hour in the market in Parachinar, capital of Kurram tribal district, local official Nasrullah Khan told AFP.
"When people rushed to the site... to rescue the wounded, a second blast took place," he said. A second official confirmed the explosions and toll.
"We fear that the death toll will increase," Khan said, adding that no further details were available yet.
The twin attacks followed a bombing earlier in the day outside the office of the police chief in southwestern Quetta, capital of the insurgency-wracked Balochistan province, that killed at least 13 people.
That attack was claimed by both the Islamic State and an offshoot of the Taliban.
The blasts in Parachinar came on the final Friday of the fasting month of Ramzan, just days ahead of Eid-ul-Fitr.
The third major attack to rock Parachinar this year, the blasts struck hours before iftar, when the streets are often crowded with people shopping for food to break their fast with the evening Ramadan meal.
Kurram is one of seven semi-autonomous tribal districts of the country, governed according to local laws and customs.
The district is known for sectarian clashes between Sunnis and Shiites, who make up roughly 20 percent of the country's population of 200 million.