Detectives are appealing for help to find two men seen outside a Bradford Co-op store minutes before it was raided by a gang of armed robbers.

A witness spotted the pair milling around in the Garforth Street area of Allerton which lies directly opposite the store in Allerton Road.

While one of the gang members stood guard at the entrance, the two other robbers herded five staff and four customers together before threatening them with handguns.

The gang escaped on foot with what police say is a large amount of money.

Detective Sergeant Richard Thornton, of Toller Lane CID, said: "These two men were seen in the area by a witness just prior to the raid.

"We are appealing for these men to come forward so we can eliminate them from our inquiries. We are also appealing for any witnesses who may have seen a vehicle parked near the store to contact police.

"Although the robbers escaped on foot they may have had a getaway car waiting. Somebody may have seen something at the time which could be vital to us now."

The robbery, which happened at 8.30pm last Thursday, prompted Peter Marks the boss of Bradford-based Yorkshire Co-operatives Limited to demand action from the West Yorkshire Chief Constable Graham Moore.

Mr Marks revealed exclusively in Saturday's Telegraph & Argus that the raid was the seventh armed robbery in one of his supermarkets in as many weeks and that he feared for his staff's safety.

He said the similarity of the raids led him to believe they were the work of the same gang.

Detective Chief Inspector Allan Doherty, head of the region's major crimes unit, has confirmed he is investigating seven attacks on Co-op stores in Bradford, Leeds, Huddersfield and Harrogate.

He said it was too early to say if they were linked but he is due to meet with Co-op representatives tomorrow to discuss safety measures.

The first man police want to trace is described as a dark-skinned African-Caribbean, aged 21-23, about 6ft 2ins tall, with short black hair who was wearing a black-sleeved sweater and gloves.

The second man is described as a dark-skinned African-Caribbean, aged 18 to 19, 5ft 4ins to 5ft 6ins tall, who was also wearing a dark sleeved jumper. He spoke with a Jamaican accent.

Anyone with information should contact Toller Lane CID on (01274) 376285.