Residents in Gloucester are being warned that scammers claiming to be police officers are targeting people in the city.

Victims have been conned out of thousands of pounds in the last few weeks with Gloucestershire Constabulary receiving seven courier fraud reports so far this month.

A total of £57,000 has been lost to the fraudsters in July. In one incident, a victim lost £40,000 over the course of several days before realising it was a scam.

The fraud involves residents being telephoned by a person purporting to be police officers from Gloucestershire Constabulary and the Metropolitan Police. These have included male and female callers who gave their names as DC Martin Riley, DC Adam Gardiner and DC Sarah Evans.

The victims are told that they are required to assist a covert police investigation, and instructed to withdraw cash and purchase foreign currency, gold, jewellery and iPhones. Victims are told that these items are needed for the secret investigation and they are instructed by the fraudsters to travel to various locations around the city; where the items are handed over to a "police courier".

Neither police nor bank officials will ever ask you to withdraw money from your account, purchase anything or hand over your personal details or passwords.

Advice to help protect yourself against scams:

• If you believe you are being targeted by a scammer hang up the phone and use a different phone line to call Action Fraud or the police, as scammers have a way to stay on the line and will pretend to be the police when you call back.

• If you don't have access to a different phone line, wait for a period of time and try calling a family member or friend first to make sure the scammer is no longer on the line.

• Just because someone knows basic details about you like your address or date of birth, it doesn't mean they are genuine bank or police employees.

• Always question suspicious phone calls and report them to Action Fraud or the police.

If you think you or someone you know has been defrauded, you can report it to Action Fraud online or by calling 0300 123 2040.