Japan's financial watchdog has started keeping a closer eye on the virtual currency market, particularly on unregistered trading.
The Financial Services Agency has issued a warning to Blockchain Laboratory, a Macau-based firm.
The firm is not registered in Japan and is believed to be offering services related to fundraising, using digital currencies known as initial coin offerings, or ICOs.
FSA officials have told the company to stop its operations targeting Japan.
The FSA says it is the first such warning following a legal revision last April that requires cryptocurrency exchanges and agencies to register with the Japanese government.
FSA officials say Blockchain Laboratory set up a website in the Japanese language to lure potential investors to ICOs.
The officials say they cautioned the firm several times, but that its response was inadequate.
They say they will consider filing for criminal charges if the firm does not comply with the latest warning.
Officials are also looking into 14 other firms in Japan and overseas that are unregistered in Japan and are thought to be offering cryptocurrency services.
Re-disseminated by The Asian Banker from NHK World