People selling vehicles, including motorcycles and quad bikes, on websites have been warned to be on their guard after a gang, believed to be based in Bradford, began targeting them.

Detectives in Bradford believe the gang, which lures victims to remote spots and robs them, has struck at least four or five times but fear there could have been more victims.

The latest incident happened at 7.45pm on Wednesday when a 25-year-old man had his van and quad bike stolen after being lured to a dead end in Wyke.

The victim, of Halifax, had advertised the £1,800 quad bike for sale and was contacted by a man who said he wanted to buy it. He was given directions to The Acres, off Summer Hall Ing, at Wyke, and drove the bike there in his Transit van, where he was flagged down by a man who said he was the buyer.

The complainant became suspicious when the ‘buyer’ kept insisting on the bike being brought out of the van and told the seller his father was fetching the money.

He decided to get back in the van but as he walked to it he was hit in the side of the face with an object, knocking him to the ground and spilling his keys.

The thief, who was with two other men, picked up the keys and drove off with the van and bike.

The victim had medical treatment, but did not need to go to hospital. His 11-year-old cousin, who was with him, was unhurt but badly shocked.

Detective Inspector Tony Nicholson, of Bradford South CID, said the incident was being linked to four or five similar offences across West Yorkshire, but centring on Bradford.

Victims have been targeted in Bradford, Halifax and Huddersfield.

Det Insp Nicholson said: “The suspects are contacting people via ebay and gumtree. They seem to be trawling the sites for heavy plant, motorbikes and quad bikes and robbing the sellers when they turn up.

“We want to warn people selling on these sites to be careful about how and where they deliver their goods to.”

He appealed for any witnesses, or anyone who recognises the suspects, to contact police.

The man who flagged down the driver was white, possibly in his mid 20s, 5ft 10-11ins tall, with short dark blond hair and a tattoo on the right side of his neck. He spoke with a Yorkshire accent. His accomplices were white, aged 20 to 25 and scruffy. One was skinny and the other of heavy build.

Anyone with information should contact Bradford South CID on 101, or Crimestoppers, anonymously, on 0800 555 111.