Bank of Tokyo-Mitsubishi UFJ, Mizuho Bank, Sumitomo Mitsui Banking Corp. and Resona Bank froze a combined total of about 3.5 billion yen in deposits as of the end of March on suspicion the accounts were being used for fraudulent purposes, officials at the Financial Services Agency said Wednesday.
The accounts are suspected of belonging to criminals, including loan sharks and swindlers. It is unclear when the banks started freezing them.
The FSA intends to use the money in the seized accounts to compensate victims of criminal financial activity.
"The government should deal with the matter promptly in a way that is helpful" to the victims, Financial Services Minister Kaoru Yosano said.
Banks can suspend or cancel customer accounts when notified by people who believe they have lost their money to the holders of the accounts.
While it is possible to compensate victims with money from the accounts by filing a civil lawsuit against the bank or the account holder, the procedure is time-consuming and locating the account holder is often impossible.
This means it is likely the bulk of the money in the suspicious accounts will remain in the care of the banks, financial observers say.