The incident took place in the poor, crowded Khurram Abad neighbourhood in Landhi.
"At least two people were killed and four others were wounded after an explosion at a cigarette shop," local police official Mohammad Khalid told AFP.
Eight motorcycles and three shops were also damaged in the blast, he said.
Bomb disposal official Abdul Hameed said initial investigations showed that the bomb was planted under a motorcycle and detonated with a timer.
Pakistan is preparing for a general election expected in May but a surge in violent sectarian attacks against minority Shia Muslims, including a bombing in Karachi last weekend that killed 50 people, has raised fears for security at the polls.
COMMENTS (4)
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I was in my office in Landhi industrial area at the time when this happened. As soon as this news came in, we were panicked and no one could analyse what would be happening in the coming few hours. Unfortunately, Karachi has become a ridiculous place to live and work.
When would we be having a 'no blast' day'?
is it a repeat of last week
Nothing New, haar rooz ke khananii !!