At least four persons were killed and 13 injured as two successive explosions hit a passenger train in Pakistan's Balochistan province.The blasts took place on a railway track in Bolan district as Jaffar Express, en route to Rawalpindi from Quetta, was passing through it, the news International reported.The first explosion targeted the locomotive of the train while the other hit a coach. The injured persons were rushed to a local hospital, a police source said.The area has been cordoned off, the source said.