Apple Senior Vice President of Worldwide Marketing, Phil Schiller, introduces the iPhone 8 during a launch event in Cupertino, California, US September 12, 2017. [Photo/Agencies]

The new phones feature Apple's first proprietary graphics processor, which provides greater speed, improved cameras and some features for augmented reality apps.

The cheapest phones have 64 gigabytes of memory, up from 32 gigabytes in previous models, and will sell for $699 and $799.

The company also introduced an upgraded Apple Watch, which can make phone calls and access the internet without the user carrying an iPhone. The Series 3 watch will cost $399.

Apple did not provide sales figures for its watches, but Cook said sales had risen 50 percent from the year before and that the Apple Watch was now the best-selling watch in the world.

Gene Munster, an analyst with Loup Ventures, believes sales of the watch could double or even triple because of the new connectivity.

The upgraded Apple TV will support the high resolution display known as 4K and will also feature more programming options as Apple steps up its efforts to cut content deals and produce its own shows.

Cook opened the event at the Steve Jobs Auditorium on Apple's new campus with a tribute to the company's co-founder and former CEO Jobs, who died in 2011.

The Apple building itself was considered to be Jobs' final product, and Cook spent a few minutes boasting about the design, energy-saving features and public spaces at the new campus, including a flagship Apple Store.

The theater, never before open to the public, features an expansive glass-enclosed lobby, with two massive white stone staircases leading down to the auditorium. Inside, the decor is similar to that of Apple's stores, with hard maple flooring and tan leather seats.

Reuters