Attempted robbery at Flinders grocery store.

Four would-be thieves attempted to rob a grocery store in Flinders at about 10.30pm on Monday night.

The unknown offenders were wearing dark hooded jackets and tracksuit pants, white gloves and white 'Scream' masks and were holding large knives.

The store's front doors were locked and could only be opened by staff with a remote control sensor.

The unknown offenders attempted to pry open the doors. When this was unsuccessful, they began banging on the glass with their fists but did not get inside.

 Lake Illawarra Police are investigating the incident. Anyone with information should call Crime Stoppers on 1800 333 000.