Apple has unveiled its first foldable iPhone at the company's annual launch event in California.

The device, called Duo, is the most expensive iPhone to date, with a starting price of $1,999 (£1,476).

Roughly the size of a passport when closed, the phone opens to reveal a 7.6in (19.3cm) screen - the largest ever for an iPhone - and allows people to use an Apple Pencil on the device - a capability previously reserved to iPad users.

The Duo enables users to split the screen to use two different apps on the device, or two windows of the same website for things like comparison shopping.

It will be available on 23 October, while the iPhone 18 Pro and 18 Pro Max - which were also unveiled at the launch - can be pre-ordered from 12 September and will start at $1,199 (£885) and $1,299 (£959), respectively.

John Ternus, Apple's new CEO, who formally took over from Tim Cook on 1 September, unveiled the foldable phone at the company's headquarters in Cupertino as part of the latest line-up of devices, saying it will "redefine the experience of using a foldable phone".

Apple said the new models feature a long battery life - 45 hours of video playback for the Pro Max - and faster charging.

The company said the camera offers "cinematic effects" from regular video captured on the phone, as well as new options for manual controls and "smart focus tracking", letting users focus on a single moving subject.

Other gadgets revealed include new AirPods headphones and a new model of Apple Watch.

'Straight out of Apple's playbook'

Apple is not the first company to develop a foldable smartphone, with several of its rivals, such as Samsung, Motorola and Google having already released foldable devices.

However, Forrester analyst Dipanjan Chatterjee insisted that releasing the device after its competitors was "straight out of Apple's playbook", which he explained involved waiting for the product to "work out its kinks" and for the market to "offer glimpses of viability".

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Ben Wood, chief analyst at CCS Insight, said the Duo was "always going to eclipse Apple's other announcements", adding that it marks the company's entry into the "niche foldable smartphone category".

Mr Wood said that while there is certain to be demand for the Duo - which costs less than some analysts had anticipated - foldable models still account for less than 5% of the overall smartphone market.

The release comes after Apple unveiled advances in artificial intelligence earlier this year, including upgrades to its Siri assistant, and emphasised a focus on privacy and day-to-day use as the company tries to catch up with rivals on AI.

In June, it was reported that millions of UK Apple customers are set to be included in a class action lawsuit against the tech giant over the storage system iCloud.

If successful, the £3bn lawsuit could see around 39.7 million people receive compensation.