Three teenagers believed to be behind scams which raised $4 million are being quizzed by Japanese police, reports said Thursday.
The trio, all 17, are thought to have been responsible for a rash of frauds across the country in which they have conned mostly elderly people into parting with large sums of money, reports citing police sources said.
The crimes, known as "It's me" fraud, involve telephoning victims and pretending to be a family member -- for example, a son -- who is in some kind of trouble, perhaps involving debt or lawyers.
Alternatively, the fraudster pretends to be calling on behalf of a family member.
The victim is asked to transfer a sum of money to help solve the problem and prevent their "son" from going to jail or falling victim to mobsters.
Despite repeated police campaigns, an astonishing number of people fall for the trick every year in Japan and elsewhere.
Commentators suggest that the often-fragmented lives of extended families, in which close relatives may not see each other for years, heightens the risks.
Tokyo Metropolitan Police made the latest arrests after a 64-year-old man and his 63-year-old wife were conned into handing over one million yen ($10,000) to help their "son" settle a dispute over getting a woman pregnant, broadcaster NHK said.
Officers swooped after another member called back seeking a further one million yen, allegedly to cover legal costs.
Police found 550 bank cards that the boys, from Tokyo and its environs, had used or planned to use to withdraw money wired from their victims' accounts, the Tokyo Shimbun said.