A trader was threatened with a nine-inch knife and robbed on April 5.

Father-of-three David Griffin had just opened up at Martin the Newsagents in Blackbird Leys Road, Oxford, at around 5.15am, and was picking up newspapers from the front of the shop when a masked raider approached wielding a knife.

The robber forced Mr Griffin inside and stood behind him while threatening him. Mr Griffin was forced to take the man to the safe and handed over about £2,000. Phone cards and cigarettes were also taken.

The robber then forced Mr Griffin to hand over the shop's CCTV video tape. The shopkeeper was pushed into a store room and locked inside.

The intruder made off through the fire exit, which triggered an alarm. Mr Griffin, 31, waited until the robber had gone before letting himself out of a back door to the store room which had not been locked.

Mr Griffin, who was unhurt in the attack, said: "I went to collect a bundle of papers from outside the shop when I was pushed back by a person wielding a knife. He was not particularly violent, just very threatening and I was extremely scared.

"He asked for the contents of the safe and wanted to be let into the cigarette cupboard -- so I did what any company advises you to do and co-operated with him."

Dc Garry Knight, of Oxford CID, said: "This was a very serious offence in which a shopkeeper was threatened with violence. It was clearly very upsetting for him.

"We would anticipate shift-workers would be travelling to work at that time of the morning, who may have seen the offender, who was possibly with an accomplice."

The raider was white, six feet tall, with short dark straight hair, of medium build, and wearing dark clothing. He is thought to be in his late 20s or early 30s. A scarf concealed the bottom of his face.

Police are not linking the incident with any other robberies.

Anyone with information should call Oxford police on 08458 505505, or the free anonymous Crimestoppers number 0800 555111.

Detectives are investigating a robbery at Bottoms Up in St Clement's Street, Oxford. The raider entered the shop and told staff he had a gun, though no weapon was seen.

He made off with a small quantity of cash.

The incident happened at about 12.30pm on April 2. The man is white, in his 20s and was wearing a dark jacket. He is well-built and wearing a distinctive, fishing-type hat.