Apple has announced that sales of its new iPhone 5S and 5C have beaten previous launches of its phones, selling nine million handsets in just three days.

In a statement Tim Cook, Apple's chief executive said: "The demand for the new iPhones has been incredible, and while we've sold out of our initial supply of iPhone 5S, stores continue to receive new iPhone shipments regularly.

Apple had taken steps to ensure the success of the opening weekend, wary of its recent struggles against strong competition with rivals.

In a notification to market regulators Apple said it expected sales in its fourth quarter to be at the higher end of its previous announced range of between $34bn and $37bn.