Man fights for life after Adelaide assault

A man is fighting for life after being assaulted at a home in Adelaide's north.

The 59-year-old was found with critical head injuries at the Hillier property after another man, 24, phoned police on Sunday afternoon.

There was "quite a bit of blood" at the scene, a police spokeswoman said, and the injured man was taken to the Royal Adelaide Hospital.

The 24-year-old is assisting police as major crime detectives investigate.