Several others were also wounded in separate attacks in Pakistan's commercial capital as the city is set to hold a by-election for a seat in the provincial assembly on Sunday, Pakistani officials said.
The seat had fallen vacant after a lawmaker of the Muttahida Qaumi Movement (MQM), Raza Haider, was killed by gunmen in August.
The killing of the MQM lawmaker triggered violence which claimed the lives of 100 people in a week.
The Muttahida Qaumi Movement is the most influential party in Karachi.
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