Japan's biggest mobile operator said Monday it will launch a translation service that lets people chat over the telephone in several different languages.

The application for NTT DoCoMo subscribers will give two-way voice and text readouts of conversations between Japanese speakers and those talking in English, Chinese or Korean with a several-second delay, the firm said.

"Hanashite Honyaku" will be a free application that can be used on smartphones and tablet computers with the Android operating system, DoCoMo said.

Customers will also be able to call landlines using the service, it said, adding that voice-to-text readouts will soon be available in French, German, Indonesian, Italian, Portuguese, Spanish and Thai.

"We hope that with this application, our subscribers will be able to widen the range of their communication," a company spokeswoman said.

However, she conceded the service does not offer perfect translations and has trouble deciphering some dialects.

DoCoMo also said it has launched a separate service that lets users translate menus and signage using the smartphone camera.