Up to 400,000 unlocked iPhones were running on China Mobile’s network at the end of last year, reports CNET.com, citing research from In-Stat. Such a scenario would go some way to explaining the so-called ‘iPhone gap’ created by the difference between Apple’s shipping totals for 2007 and the activations reported by its operator partners in the US and Europe.

Last month China Mobile – the world’s largest mobile operator by subscribers – was reported to have ended talks to sell Apple’s iPhone in China, citing an inability to agree on revenue-sharing terms. The device is currently available via exclusive operators in the US (AT&T), France (Orange), Germany (T-Mobile) and the UK (O2). The iPhone is set to make its official debut in Asia at some point this year. In recent months Telstra of Australia and South Korea’s KT Freetel have said they are also in talks with Apple on bringing the iPhone to their countries.