NHK has learned that someone used an IP address to repeatedly access illegally-opened accounts for mobile phone carrier NTT Docomo's cashless payment service last month.
The Docomo service allows people who register their bank account information to make purchases and transfer money.
Japan's finance minister says he wants an operator of an e-money service and banks to put top priority on protecting depositors, following a major fraud case.
Aso Taro was speaking on Friday following revelations that bank customers had their savings stolen by scammers who abused telecom giant NTT Docomo's cashless payment service.
NHK has learned that 34 users of the e-money service of mobile carrier NTT Docomo have had a total of 10 million yen, or over 94 thousand dollars, illicitly withdrawn from their bank accounts as of Wednesday.
NTT Docomo says it will enter discussions on compensating the victims with the banks in question.