A SHOP assistant has described the terrifying moment when she encountered a masked, knife-wielding man behind a Swindon shop.

The 23-year-old woman, who is too distressed to be identified, was confronted by the man when she went to the back of the One-Stop shop in Guildford Avenue, Lawn, about 6.20am on Tuesday.

The would-be robber fled the scene empty-handed after her screams attracted the attention of the shop manager and the victim is now helping police with their inquiries.

She said: "I had gone to get an empty trolley.

"At first I saw nothing but as I turned around someone was there. I was just really scared, screaming. He just stood there, with his face covered, and he had a really big knife.

"My manager came running out and I ran back into the shop, rang the police and locked myself in an office. I was crying and shaking, and I was sick."

Police arrived at the scene immediately and carried out a full search of the area.

Woman Detective Constable Em Matthews of Swindon CID is not linking the offence to any other incidents.

She is particularly keen to speak to anyone who may have been in the shop on Tuesday morning between 6am and 6.30am.

Police have also released a CCTV image of a cyclist seen in the area just before the incident, so that they can eliminate him from their inquiries.

WDC Matthews said: "It was a pretty nasty incident. Naturally the young woman was very distressed by her traumatic ordeal and we would urge anyone with information to get in touch."

Though the woman remains in shock, she was back at work yesterday after being supported by her work colleagues, family and police.

The man was about 5ft 10ins tall and wore either a stocking or tights over his head, covering his face.

He also wore a dark anorak, blue jeans, white trainers and a hood which was either attached to the jacket or to a top underneath.

Anyone with information, even if they do not think it significant, is asked to call the police on Swindon 528111 or Crimestoppers on 0800 555111.

All calls will be treated in strict confidence.

A man was arrested near the shop and, after questioning, was released on police bail pending further inquiries.