The Co-op, on Stock Road, Billericay, was targeted last night, at around 9.20pm with thousands of pounds being stolen.
A man went into the store and demanded cash, before making off with thousands of pounds.
An Essex Police spokesman said:
“No weapon was seen and no-one was injured. We are investigating whether or not this may be linked to similar incidents in other parts of the county. If you saw anything, were driving in the area and have any dashcam footage, or have any other information please call us on 101 quoting the crime reference number 42/46841/18. Alternatively you can call Crimestoppers anonymously on 0800 555 111.”