Two men brandishing machetes and crowbars are being sought after the armed robbery on High Street in Gorseinon, Swansea, on Tuesday morning.
They fled empty-handed in a grey Audi A3 S Line, which was later found burnt out on Coalbrook Road, Grovesend.
Witnesses said the robbers “came through the ceiling” and held a member of staff by the throat.
However, South Wales Police said no-one was hurt in the day-time raid.
The men, dressed in overalls with their faces covered, escaped via a lane behind the Lloyds Bank branch just after 10:00 GMT.
They then turned right on to Brighton Road, before turning left on to Cecil Road. From there, the suspects are believed to have turned right on to Pontarddulais Road and then turned in to Coalbrook Road, where the car was discovered abandoned and set alight.
Police are appealing for information, particularly from anyone in these areas between 07:00 and 11:00.
Det Insp Matthew Davies said: “Our enquiries are ongoing. In particular, I’d like to hear from anyone who saw a vehicle matching this description or who witnessed anything suspicious.
“Alternatively, anyone with dash-cam, cycle-cams or private CCTV is urged to check their footage and make contact.
- Bank robbers ‘came through ceiling’
“I’d also issue an appeal directly to residents of the Grovesend area.
“Did you see the vehicle in the area between around 10.30am and 11am? Or perhaps another vehicle which was being driven at speed or suspiciously in the area?”