Four masked men robbed a Post Office and forced a worker to open the safe.
The men struck just before 3pm at a Post Office in Lower Horsebridge, near Hailsham, yesterday and "threatened" a male member of staff, ordering him to open the safe.
They made off from the Post Office with thousands of pounds and 2500 euros.
They ran from the shop and climbed into a waiting red Alfra Romeo Brera that drove off towards Hailsham.
The car is believed to have been stolen during a burglary of a house in Cowbeech, Rushlake Green, a short time earlier.
The car had been seen at the property as recently as 1.30pm.
Detective Inspector Mark O'Brien said: "The car hasn't yet been found and we are very interested to hear from anyone who may have seen it at any time from after 1.30pm in Rushlake Green or seen in the locality of the Post Office in Horsebridge.
"It was seen to head off towards Hailsham, but in reality may have ended up going in any direction, it may have been driven fast or erratically and you may have noticed that.
"It is also likely that the vehicle has now been abandoned by the criminals. So if you saw a red Alfa Romeo or the occupants, we'd like to hear from you.
"I'm pleased to say that the member of staff who was threatened by the men was not hurt, but he was understandably very shaken. No weapons were seen, but the men were very vocal and threatening in their behaviour.
"I'd like to hear from anyone who can provide us with any information about this incident. Please email firstname.lastname@example.org or call 101 quoting serial 894 of 14/08. Alternatively, call the independent charity Crimestoppers anonymously on 0800 555 111."