Apple said Monday that it had sold more than four million new iPhone 4s models in their first three days on the market.
Sales took off as the greatly upgraded version of the iPhone 4 was released to the market on Friday in seven countries: the United States, Australia, Canada, France, Germany, Japan, and Britain.
Apple said more than 25 million customers have adopted its brand new mobile operating system -- included in the 4s -- called iOS5, and that 20 million have signed up to use its iCloud cloud computing, or online data storage, system.
The 4S was launched on October 4, one day before visionary Apple co-founder and longtime Steve Jobs died following a long battle with cancer. His health failing, Jobs had stepped down as chief executive in August and was replaced by Tim Cook, who presided over the launch of the new iPhone.
It will be available in 22 other countries, including much of Europe, by the end of October, and more than 70 countries by the end of 2011, Apple said.
Explore further: Apple to unveil iPhone 5 on October 4: report