Suspected Sunni militants bombed a bus carrying Shiite worshippers and two hours later attacked a hospital treating the victims, killing 25 people and wounding 100 Feb. 5 in a strike on Karachi, Pakistan's largest city.

Prime Minister Yousuf Raza Gilani appealed for calm in the city, which is the country's commercial heart. It has a history of religious violence between Shiite and Sunni Muslims, and has been tense in recent weeks due to clashes between rival political parties that have left dozens dead.

In late December, extremists in the city detonated a bomb that killed 44 Shiites during a procession to mark Ashura, the anniversary of the death of revered Shiite figure Imam Hussein, sparking the city's worst riots in recent years. The Feb. 5 blasts coincided with Arbaeen, the final day of the annual 40-day mourning period for Hussein.

Shiites marking Arbaeen were also targeted in Iraq on Feb. 5. A suicide attacker detonated a car bomb alongside a crowd of pilgrims walking to the holy city of Karbala, killing at least 27 people.