Apple said more than 50 per cent of compatible devices are already using iOS 9, marking the “fastest iOS adoption ever” following the launch of the platform last week.

“iOS 9 is off to an amazing start, on pace to be downloaded by more users than any other software release in Apple’s history,” said Philip Schiller, SVP of worldwide marketing at Apple.

The announcement came as it also said that its latest-generation iPhones, iPhone 6s and iPhone 6s Plus, will be available in some markets from Friday. The devices, unveiled earlier this month, see the introduction of a pressure-sensitive touch screen and new camera, alongside a host of other updates.

In initial market availability is focused on Australia, Canada, China, France, Germany, Hong Kong, Japan, New Zealand, Puerto Rico, Singapore, UK and US.

While iOS 9 may have got off to a strong start, the same cannot be said of the update to Apple’s watchOS, which was pulled due to the discovery of a “bug” that is “taking a bit longer to fix than we expected”.