Pre-orders for the iPhone 4 exceeded 200 thousand units, shortly after it went on sale Saturday.

China Unicom, the sole operator of Apple's iPhone in China, says it's already stopped taking online orders because of strong demand. The iPhone 4 is being offered through China Unicom on a two-year contract, and also through Apple retail stores in China. About 60 thousand buyers have received phones through China Unicom so far.

Apple is planning to open more retail stores in China, to capitalise on the world's largest mobile phone market, with more than 800 million subscribers.