Pakistani officials say at least 49 people were killed and more than 30 wounded on January 30 in a bombing at a Shi'ite mosque in the southern province of Sindh.
The bombing occurred in the Lakhi Dar area of the town of Shikarpur, some 470 kilometers north of Karachi, during Friday prayers.
The Sunni militant group Jundallah claimed responsibility for the attack.
Sunni Muslim extremists have often targeted religious institutions of Shi'a, whom they do not consider to be true Muslims.
The port of Karachi, which is Pakistan's largest city, is rife with criminal, ethnic, political and sectarian killings that claim hundreds of lives.
The attack was one of the deadliest in Pakistan since Taliban militants seized a mlitary-run school in the northern city of Peshawar on December 16 and killed 151 people, almost all of them children.