At least three people were killed and Five others injured when a powerful bomb blast at a television network office in Karachi, officials said Friday.According to details, a powerful blast occurred in Old Muzaffarabad Colony in Landhi area near Rangers Headquarters on night between Thursday and Friday, killing three people and wounding three others.The blast occurred near a television network office which also damaged the office and a motorcycle parked near-by.According to SP Raja Umar Khitab, two kilogram explosive material was used in the blast. Governor Sindh has taken notice of the incident and sought report from IG Sindh with 24 hours.On the other hand, four people were injured in when a gas cylinder of a mini bus exploded near Korangi crossing.