Opening weekend sales of Apple’s fifth-gen smartphone, the iPhone 4S, have topped 4m units, claims senior vice president of Worldwide Product Marketing Phil Schiller.

“iPhone 4S is off to a great start with more than four million sold in its first weekend,” commented Schiller, who also said that sales are more than double than that of the iPhone 4 launch during its first three days.

The iPhone 4S, which comes pre-loaded with hundreds of new software improvements and free iCloud storage, launched on October 14th with queues of people lining up outside Apple stores to the be the first to get their hands on the smartphone.

Demand was high at launch day at Apple’s Regent St. Store

The demand for the iOS 5 device has resulted in delays with preorders. Apple has confirmed that orders placed online today may not be with customers for two weeks. Early reports also indicate that 16GB iPhone 4S units are most in demand with many Apple stores running out of stock.

The iPhone 4S will roll out worldwide to 22 more countries by the end of October, including Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, Hungary, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Mexico, Netherlands, Norway, Singapore, Slovakia, Slovenia, Spain, Sweden and Switzerland.

For more details on prices and features check out the official press release.