In one case, a couple were duped into handing over £65,000 after being convinced they were helping police to carry out an undercover investigation.
The gang also used a cunning phone trick to dupe another woman into handing over her bank card details so they could steal thousands from her. They then laundered thousands of pounds through banks and travel agent stores in shopping centres around Glasgow by turning the cash into euros.
Four members of the gang have now been jailed after they admitted a series of offences "aggravated by a connection with serious organised crime".
The Crown confirmed those jailed were almost certainly part of a wider international conspiracy.
The gang - who took time to thank their victims for their help - left one woman so distressed she became ill, suffered nightmares, and died a few months after losing her life savings.
Fiscal depute John Malpass told Perth Sheriff Court: "There has been a large scale police operation into investigating these crimes.
"The exact scale of the scheme is not known, but there are similar investigations in England, and the transfer of money to euro suggests the scheme may go beyond the UK."
At the head of the Scottish leg of the gang was Azeem Mohammed, who was captured by detectives because of links to the telephones used to con the victims.
Mr Malpass said Mohammed was part of a group of men who duped Perth couple Matthew Miller, 90, and wife Martha, 88, into handing over £65,000 in cash to a fake policeman.
The court was told Mrs Miller later died after the stress of the theft aggravated her diabetes.
The calls to the couple were linked to a phone belonging to Mohammed.
Mohammed, 22, of Allison Street, Glasgow, was jailed for 34 months.
Sheriff Michael Fletcher told him: "These despicable offences were committed by you against extremely vulnerable people entitled to think they were safe in their own homes and that their savings were safe in the bank.
"You preyed on their vulnerability. In doing so you succeeded in obtaining very substantial sums of money from their accounts.
"These offences cause extreme upset."
Latvian Igors Rimars, 38, of Rosemount Square, Aberdeen, was jailed for 12 months after being previously found guilty of money laundering offences in Aberdeen in October 2011.
Laura Copleton, 24, of Barfillan Drive, Glasgow, was jailed for nine months for money laundering in Glasgow by receiving some of the cash into her account.
Emma Cunningham, 20, of Corbiston Way, Cumbernauld, was detained for seven months after she admitted two charges of using the bank card details of 81-year-old Perth resident Helen Henderson at Silverburn shopping centre in September 2011 to obtain more than £4000 in euros.
Two other members of the gang, Latvian Imants Zacs and David McKissock, had previously been sentenced by the court, but reporting restrictions were only lifted yesterday.
Zacs, from Aberdeen, admitted having forged documents, and was ordered to carry out 300 hours' unpaid work, while McKissock, from Glasgow, was jailed for 20 months for money laundering.