Detectives were today hunting a robber who held a woman shop worker at knife-point in a terrifying raid, write Emma Henry and Phil Clee.

The man walked into the New Plus store in Jericho, Oxford, yesterday and grabbed his victim, holding the blade against her neck.

The robber struck just after 1.15pm and police say he had been in the shop five minutes earlier.

He grabbed cash from beside the till and fled, leaving the woman shocked but unhurt. The amount of money stolen has not been disclosed. A police spokesman said: "This was a frightening experience for this shop employee and it's a matter of urgency that police track down the person who did this."

The raider may have deliberately picked the woman. On his first visit to the Kingston Road store he was served by the male shopkeeper and only returned when the woman was behind the counter.

Police said the man was in his 20s, 5ft 6in tall and of medium build. He is described as either Oriental or white with a suntan. He was wearing a blue cotton hat and brown anorak. The robbery was the latest in a series of attacks on Oxfordshire shops.

Two weeks ago, a gang wielding iron bars raided the sub-post office at Nuneham Courtenay, smashing their way through security panels and threatening the postmaster before grabbing cash.

Seven days earlier, a robber armed with a handgun and meat cleaver attacked a shopkeeper in broad daylight at the Londis shop in St Clement's, Oxford.

Last month, two men armed with a gun raided the Glanville Road post office in east Oxford. They grabbed cash and struck a four-year-old child as they fled. Days earlier, Cholsey postmistress Pat Kinch and her husband Eddie were threatened with a carving knife during a raid.

Anyone with information is asked to contact police on 01865 266333.