Robbers fled with money after a raid on Cubbington Post Office this morning (Monday October 24).
The robbery happened in Queen Street, Cubbington, between 5.30am and 6am and police are appealing for witnesses to come forward.
Detective Sergeant Tristan Pettitt said: "Though I am glad to report that no one was hurt, this was a shocking incident that remains rare in the town.
"We are working hard to catch those responsible and we are asking anyone with any information to come forward.
"Did you see anything in the area, before, during or after that time frame?
"If so, please get in touch by calling us on 101, citing incident 53 of October 24."