Two bombs exploded in Karachi on Friday, one outside a hospital treating victims from the earlier attack on mourners, leaving 25 dead and dozens of others injured, report said. Police appealed for calm following the strikes in Karachi, which took place within two hours of each other. The chaotic city of 16 million people has a history of religious violence and has been tense in recent weeks due to deadly clashes between rival political parties. In late December, a bomb killed 44 Shiites attending a procession in the city, sparking riots. The first blast on Friday targeted a bus carrying worshippers, most of them women and children, killing 13 and wounding 49, officials said. The bomb was attached to a motorcycle and detonated as the bus drove to a religious procession held in connection with the Arbaeen holy day that marks the end of 40 days of mourning after the anniversary of the death of Imam Hussein (RA).