A blast killed 24 people and injured 70 in the northwestern Pakistani city of Parachinar on Sunday, officials said, and a banned Sunni group claimed responsibility for the attack.
Parachinar local government official Riaz Hussain said Sunday's blast targeted crowds at a market.
"The death toll has reached 24 and 70 are wounded," said Amjad Ali Khan, the political head of Kurram Agency. Parachinar is the capital of Kurram, and has been the location of attacks in the past.
"Some of the injured are in critical condition," said Shafiq Hussain, a health worker at the Agency Headquarters Hospital Parachinar.
"This is revenge for the killing of Muslims by the Syrian president and Iran," said Ali bin Sufyan, spokesman for Lashkar-e-Jhangvi (LeJ), an armed group whose sectarian ideology is closely aligned with that of The Islamic State in Iran and the Levant (ISIL). He spoke to Reuters by phone.
LeJ, whose roots are in Punjab province, wants to expel Shias from Pakistan, where minority Shia Muslims make up about 20 percent of the 180-million population and sectarian attacks are on the rise. Groups such as LeJ say they are fighting for a Sunni theocracy and that Shias who do not leave Pakistan should be killed.
LeJ has suffered a series of setbacks this year.
The leader of LeJ, Malik Ishaq, along with his two sons Usman and Haq Nawaz, and several top officials were shot dead in police custody this July; police say they were trying to escape. Last month another top LeJ commander was shot by police while in custody.
The group Ishaq founded has claimed responsibility for the deaths of hundreds of civilians, most of them minority Shia Muslims.
Al Jazeera with Reuters