Wodonga Detective Leading Sen-Constable Aaron Ibbott said at 5am, an employee at the Shell service station went to check if the outside toilets needed cleaning.

Sen-Constable Ibbott said the attendant confronted a man outside the Main Street business after he spotted him rifling through the till inside.

During the confrontation, the attendant was hit with a hammer on his arm before the offender fled with cash to the west at the rear of the service station.

The attendant did not suffer serious injuries.

Sen-Constable Ibbott said a number of Rutherglen residents were walking their dogs at the time of the theft and assault and may have seen the offender fleeing.

The attacker was in his mid-20s, 180 centimetres tall with an athletic build and he was wearing a black-hooded jumper with a small white emblem on the front and a larger white emblem on the back, as well as army green shorts and runners.

Sen-Constable Ibbott asked anyone who saw a man matching this description to come forward and help with the investigation.

He asked anyone who has information about the theft and assault to also contact police.

Information can be given anonymously to Wodonga police on (02) 6049 2600.