Police are hunting a masked man who entered a garage in Cardiff armed with an axe and threatened staff before demanding cash from a till.
The incident happened around 0040 BST on Monday at the Co-operative garage on Llantrisant Road in Llandaff.
Officers, who are studying CCTV footage, said although money was taken no one was injured.
A spokesperson for The Co-operative said: "The members of staff were unharmed but badly shaken."
Anyone with information is asked to contact Fairwater CID on 02920 527248 or Crimestoppers on 0800 555111.