Three backpackers have been killed and another has been flown to hospital with life-threatening injuries after a crash in northern Victoria early on Sunday.

The 21-year-old male German driver and two passengers – both 21-year-old Canadians – were killed instantly when their Ford station wagon flipped on a single-lane road at Dingwall, near Kerang.

A 19-year-old British man was flown to the Royal Melbourne Hospital with critical injuries, and a fifth passenger – ​a 29-year-old German man – is being treated for non-life threatening injuries.