KARACHI, Pakistan – A car bomb exploded outside a mosque on Sunday, killing 37 people and wounding another 141 in a Shiite Muslim dominated neighborhood in the southern Pakistan city of Karachi – the third mass casualty attack on the minority sect in the country this year.

No one has taken responsibility for the bombing, but Shiite Muslims have been increasingly targeted by Sunni militant groups in Karachi, Pakistan's economic hub and site of years of political, sectarian and ethnic violence, as well as other parts of the country.

The bomb exploded outside a Shiite mosque as people were leaving evening prayers in Pakistan's largest city. Initial reports suggested the bomb was rigged to a motorcycle, but a top police official, Shabbir Sheikh, said later that an estimated 100 kilograms (220 pounds) of explosives was planted in a car.