At least 15 people have been killed in a blast in the volatile Pakistani city of Karachi, officials say.At least 30 people are reported to have been wounded in the explosion in Pakistan’s main commercial city.Police say the blast was caused by a bomb which rocked an illegal gambling den that officials say is operated by a local crime gang.The attack took place in the Lyari neighbourhood, where a number of warring drug and arms gangs operate.”We have received fourteen bodies so far and several more people are injured,” Hamid Parihar, Karachi’s police surgeon, The city has seen a series of political and ethnic attacks. Criminal gangs are said to be involved in the violence, which claimed 775 lives last year.