Two men escaped with more than £560 of cigarettes last night in Worthing's 17th robbery since Christmas.
The raiders burst into Dominion News, in Dominion Road, and jostled the owner before making off with the haul.
The owner was unable to describe the two men, who remained behind him throughout the raid.
He said they warned him: "Don't follow us or we'll blow your head off."
Police could not confirm whether the two men were actually armed.
Detective Constable Dave Dowell, of Worthing CID, said the threat suggested firearms may have been involved but the victim didn't see any weapons.
He said anyone offered cheap cigarettes should contact the police.
The robbery happened at about 7pm last night when the owner was at the rear of the shop bringing in new stock.
It has taken the tally of robberies on shops and businesses in the Worthing area up to 17 since Christmas.
Anyone with information should contact Mr Dowell on 0845 6070999.
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