The Texaco garage on the A335 Southampton Rd has been subject to the second armed hold up in three months.
The latest incident occurred just after 3am on Monday, March 29.
A night-time cashier was on duty when the man came up to the window and threatened the cashier with a small hand-gun and demanded he hand over the contents of the till. When the cashier refused, the offender ran off.
He is described as white, aged 20 -25 years with a slim build and black hair.
He was wearing dark blue jeans, a black hooded anorak and black trainers.
Police have issued the following E-fit and CCTV image of the suspect.
Officers are keen to speak to anyone who was in the area at the time of the incident and may have seen someone matching the offender’s description, or knows who he might be.
Anyone with information is asked to contact Eastleigh CID on 101 or the Crimestoppers charity line anonymously on 0800 555 111.
It was on New Year’s Eve that a suspect armed with a handgun struck at the same garage forcing a terrified night cashier to hand over the contents of the till before making off.