Police are investigating the death of an off-duty Australian soldier who was killed by a truck and trailer near Christchurch.

The soldier, who had been working with the New Zealand Army, was walking along State Highway 1 near Rolleston when he was hit about 12.30am on Saturday.

He died at the scene, police say.

The driver of the truck has been interviewed and police investigations are continuing.

The New Zealand Defence Force says the man's next of kin have been informed.