Apple has announced that sales of the iPhone 3G topped one million on Sunday, just three days after launch.
"It took 74 days to sell the first one million original iPhones, so the new iPhone 3G is clearly off to a great start around the world," said Apple CEO Steve Jobs.
Apple also said that iPhone and iPod touch users have downloaded more than 10 million applications from its new App Store since its launch late last week.
According to a report by The Guardian, RBC Capital Markets analysts believe that buyers will be frustrated by limited stock and logistical problems caused by launching across 28 mobile operators in 22 countries. Nevertheless, they expect Apple to achieve overall worldwide sales of 5.1 million iPhone 3Gs by Q3 2008.
iPhone purchasers in the US were unable to use their new phones for several hours because the iTunes store - through which users administer their accounts - was weighed down by requests.
In the UK, O2 - the exclusive mobile retailer for iPhone - saw its web-based retail system collapse on Friday, making it impossible to register and sell new handsets. The problem persisted into Saturday when stores were unable to sell the new phones, despite adequate stock.
Apple is expected to meet its target of launching the new 3G handset in 70 countries, said RBC analysts, and will sell around 14 million iPhones in the next year.