A large volume of English-language junk emails marketing impotence drugs has been circulating in Japan, the Internal Affairs and Communications Ministry said.
The agency said this is the first confirmed instance of English-language junk emails sent to mobile phones.
The agency further reported that Japan's mobile carriers have launched anti-spam efforts following the discovery of the spam.
Mobile phone carrier Softbank has introduced a system that enables users to block unsolicited emails and is urging its mobile phone users to change the settings on their mobile phones to use the system.
According to Softbank, there are several versions of English-language emails touting male impotence drugs. If a user accesses the address on the email, a page is displayed listing the types of drugs and prices.
NTT DoCoMo and KDDI, which run the au and Tu-ka services, respectively, are also examining measures to counter English-language junk emails.