Apple's water-resistant iPhone 7 and 7 Plus go on sale

Apple's latest smartphone, the iPhone 7, goes on sale alongside a new version of the Apple Watch today, with smaller queues than previous years expected outside the tech giant's retail stores.

The iPhone 7 and 7 Plus will both come in two new black finishes and are water resistant for the first time.

But some industry experts have questioned the need to update to the new device ahead of a major upgrade expected in the 10th anniversary iPhone due to be released next year.

However, Apple revealed on Thursday that the iPhone 7 Plus, which comes with dual rear cameras for the first time, has already sold out in all colours during the pre-order period, while the polished Jet Black finish iPhone 7 will also not be available to walk-in customers on launch day.

This announcement is likely to also affect the size of queues outside stores.

"We couldn't be happier with the initial response to the iPhone 7 and iPhone 7 Plus, and we are looking forward to beginning sales through our retail stores and partners around the world," Apple's statement said.

"Beginning Friday, limited quantities of iPhone 7 in silver, gold, rose gold and black will be available for walk-in customers at Apple retail stores.

"During the online pre-order period, initial quantities of iPhone 7 Plus in all finishes and iPhone 7 in jet black sold out and will not be available for walk-in customers."

Upon announcing the new device earlier this month, Apple boss Tim Cook said the tech giant's aim was to create the "most advanced smartphone" it has ever made.

The iPhone 7 also sees the removal of the device's headphone jack, with users now needing to connect headsets via the Lightning port, or use wireless headphones.