Six men were arrested after police investigating fraud raided several addresses.

The men were arrested between January 28 and January 30 at different homes on suspicion of taking over £1million from victims in Watford, Bushey and various other areas across Hertfordshire.

The fraud incidents involved bogus phone calls which scammed people into giving money.

Warrants were served as part of the wide-ranging investigation by Hertfordshire Constabulary’s Serious Fraud and Cyber Unit, alongside officers from Kent Police’s Directorate, Met Police, City of London Police and North East Regional Special Operations Unit.

All the men arrested were released while investigations continue.

Detective Inspector Rob Burns, from Hertfordshire Constabulary’s Serious Fraud and Cyber Unit, said: “Courier fraud has been on the increase across the country and we have been carrying out intensive investigations to track down those responsible.

“Working with our partners in other forces and agencies, we have the capabilities to track and detain fraudsters wherever they are operating.

“It’s important to remember that police officers and bank officials will never ask you to withdraw money, purchase goods or hand over private banking details.

“Please help us to raise awareness by sharing this with your friends and family, especially if they are vulnerable or elderly.”

The constabulary also offered advice to prevent fraud through phone calls including to be sceptical, never give personal information and to opt out from many cold calls by registering with the Telephone Preference Service on 0845 070 0707.

The men who were arrested and later released were:

• A 19-year-old man from Tower Hamlets

• A 20-year-old man from Westminster

• A 21-year-old man from Mile End

• A 22-year-old man from Mile End

• A 24-year-old man from Camden

• A 31-year-old man from Camden