Police are asking for "critical witnesses" to help them hunt offenders from a fatal assault at an Auckland bus stop, on Saturday

A US PHD student died after suffering serious head injuries on Meadowbank's St Johns Road about 10pm

Police are hunting at least two offenders - and asking for witnesses and dashcam footage.

Detective Inspector Glenn Baldwin says they want information on a black SUV in the area about 9.50pm.

He says they especially want to speak to people in a white Toyota ute cut off by the SUV - when it did a U-turn on St John's Road.

Baldwin says he's confident they'll remember because they saw some pretty erratic driving.