Pakistani security forces on Tuesday said they had killed three suspected militants in Quetta city, the media reported on Tuesday.The dead in the targeted operation on Monday night included the Balochistan chief of the banned Jaish-ul-Islam group, Mehmood Rind, an officer said. Two security personnel too were injured in the "intense exchange of fire", the officer added.Police and Frontier Corps launched a crackdown against militants in different areas of Quetta and arrested 39 suspects early on Tuesday.