At least four persons were killed and about 50 injured in two separate accidents involving four passenger trains amid dense fog near Kanpur within an hour early on Saturday. The Delhi-Allahabad Prayagraj Express was at the Panki Railway station when the Gorakhdham Express hit it from behind in dense fog. In another accident, the Delhi-bound Licchavi Express rammed into the stationary Magadh Express at Sarai Bhopat near Etawah.