One person was killed and six including children were injured in a gas cylinder explosion in Pakistan's southern port city of Karachi on Wednesday, the police said.The incident happened inside a multi-storeyed building in Lyari area of Karachi, the provincial capital of southern Sindh province, police officials told local media.The residential building was also partially damaged due to the cylinder blast, said the police, adding that it might have happened due to a gas leak, Xinhua news agency reported.The injured people have been shifted to a nearby hospital and are being treated for severe burn injuries.