Police say a bomb blast outside a cable TV office in southern Pakistan has killed three people and wounded four others, The Associated Press reported.

Police officer Sadaqat Ali said Friday, March 15, the bomb was planted in a rickshaw and went off after midnight in Pakistan's largest city, Karachi.

He says the motive behind the bombing was unclear, and police are investigating.

Karachi is a sprawling metropolis of roughly 18 million people and has a long history of political, sectarian and ethnic violence.

The latest bombing comes two days after gunmen shot and killed Perween Rahman, a pioneering female activist who helped bring services like sewers and water to the city's poorest neighborhoods.