Bank customers have reported having hundreds of pounds swiped from their accounts at cashpoint machines in Hampstead and Kentish Town.

Police have warned people to be extra vigilant to avoid falling victim to fraudsters operating in the area.

Hampstead mum Klio Ftika told how she fell victim to the scam on Wednesday as she was taking out cash at the machine in the Sainsbury’s car park in the O2 shopping centre in Finchley Road.

She said: “I tried to withdraw money from the cash machine but, unfortunately, my card was withheld. I thought it was because of a malfunction and I made the huge mistake to leave the machine and go inside the store to ask for help. As it turned out somebody stole my card while I was inside the store.

“I am pretty confident the machine is tampered with as apparently my pin was also taken. I had my card cancelled within 30 minutes but I was shocked to find out that a good amount was already withdrawn. Just be extra careful there!”

Izabela Maria Suchomska added: “Please all be extremely vigilant when using the HSBC machine opposite Finchley Road tube station, my work colleagues had a card swallowed and money stolen. Always try to go inside a branch if possible. In fact yesterday I foolishly tried to use that very HSBC machine but checked the slot and it was so loose that by touching it was pushed in. It clearly was tempered with too.”

Another mum Bronwyn Boumendil said her card was held by the same machine last night so she cancelled it straight away.

Sarah-Jane Biggs saud same thing happened to her mother at a Post Office cash machine in Brecknock Road, NW5.

She said: “My Mum had exactly the same thing happen to her yesterday but in Camden. They withdrew £500 literally within five minutes of her card being ‘withheld’ by the machine! My Mum also walked away from the machine to seek help. We were on the phone to the bank cancelling the card within two minutes but these people clearly work quickly. They must have machines that allow the card to be ‘swallowed’ and ‘pushed’ back out for the thief to take.

Please can we spread the word to tell our friends to only withdraw cash from machines inside the bank or on a busy high street where other people can help stop the culprits?”

She added: “I’m a little surprised the actual bank staff are not checking the outside machines for evidence of tampering.”

A police spokesman said: “If there is anything unusual about the cash machine or there are signs that it has been tampered with, do not use it and report it to the bank as soon as possible.

“Fraudsters sometimes fit devices to cash machines that trap your card, or ‘eat’ it, which they then retrieve as soon as you have left the area. If your card is retained by the machine for any reason, report it to your card company immediately - ideally using your mobile phone while you’re still in front of the machine. Make sure you have your card company’s 24 hour contact number stored in your mobile phone.”

An HSBC UK spokesperson said: “HSBC UK takes fraud & other financial crimes very seriously. We try to protect our ATMs from fraud but criminals have been known to tamper with them. Stay vigilant and if you spot anything unusual, or if there are signs of tampering, don’t use it.”

Sainsbury’s has been contacted for a comment.