Earlier we already told you that Apple will update Siri to support more languages including Japanese, Chinese, Korean, Italian, and Spanish. But now people are reporting that Siri told them that Siri can speak Japanese. However, Japanese is not available as a choice in the Siri preferences pane… Looks like Apple is slowly updating Siri to support more languages.

Language Support and Availability

Siri works exclusively on iPhone 4S. Siri understands and can speak the following languages:

• English (United States, United Kingdom, Australia)
• French (France)
• German (Germany)

In 2012, Siri will support additional languages, including Japanese, Chinese, Korean, Italian, and Spanish.

Can I use Siri in any of these languages in other countries?

Yes. Siri can be enabled in any country, and you can choose to speak to it in English, French, or German. However, Siri is designed to recognize the specific accents and dialects of the supported countries listed above. Since every language has its own accents and dialects, the accuracy rate will be higher for native speakers.

Source [macrumors and 9to5mac]