Suicide bombers on motorcycles blew themselves up within a minute of each other outside Shi'ite mosques in a volatile Pakistani town near the Afghan border on Friday, killing at least 39 people, officials said.
Sectarian violence has been on the rise in nuclear-armed Pakistan, where hardline Sunni militant groups have been relentlessly attacking Shi'ites whom they see as heretics.
The first explosion took place meters away from a Shi'ite mosque near a busy market in Parachinar, capital of the tribal Kurram area. It was followed shortly afterwards by a second blast, close to another mosque in the town.
Riaz Mahsud, the top administrator of the Kurram region, said 39 people were killed and 72 wounded, adding that the attacks were carried out by suicide bombers on motorbikes.
"Some of the injured are still in critical condition and have been shifted to the main hospital in Parachinar," he said.
It was unclear which group carried out the attack and no one immediately claimed responsibility. Shi'ite Muslims make up a little over 10 percent of Pakistan's population of 180 million.
Parachinar itself is home to a significant Shi'ite community which has been previously targeted by Sunni militants.
Pakistan has suffered a spate of bombings since Prime Minister Nawaz Sharif was sworn in last month, underscoring the challenges he faces in taming sectarian violence as well as an escalating Taliban-linked insurgency.
Sabir Hussain, a doctor at the Agency Headquarters Hospital, earlier said 15 dead bodies and 45 people with serious wounds had been brought to his hospital.
Both explosions took place before sunset just as people flocked to the market area to buy food for their evening meals after a day of fasting during the holy month of Ramadan.
"A lot of people usually throng roadside markets in Parachinar before sunset for Iftar (dinner) shopping," said tribesman Haider Ali. "Hundreds of people were present during the blasts and that's why the death toll was high."