Apple unveils iPhone 4 at WWDC

The iPhone 4 has a new touch-screen display dubbed Retina

Apple has confirmed weeks of speculation with the introduction of a new iPhone handset.

Chief executive Steve Jobs unveiled the model during his keynote at the Worldwide Developers Conference in San Francisco, describing it as the biggest upgrade to the line since its release in 2007.

Central to the iPhone 4 is a new touch-screen display dubbed Retina that supports resolutions up to 960 x 640. Other hardware upgrades include extended battery life, a three-axis gyro and front and back-mounted cameras.

The handsets run the fourth incarnation of the iPhone OS, which Apple now calls iOS4. The firmware update was unveiled in April, and adds support for multi-tasking and folders.

IOS4 also supports FaceTime video chat, a Wi-Fi service that allows iPhone 4 users to connect and chat through the handset's front-mounted video camera.

The back-mounted 4-megapixel camera is capable of shooting HD video, and movie clips can be edited through an optional mobile iMovie application.

"FaceTime video calling sets a new standard for mobile communication, and our Retina display is the highest resolution ever in a phone, with text looking like it does on a fine printed page," said Jobs. "We have been dreaming about these breakthroughs for decades."

The iPhone 4 will arrive in the US and UK on 24 June, and pre-orders open on 15 June. The 16GB model will retail at $199 (£137) and the 32GB model at $299 (£206). The 8GB iPhone 3GS will cost $99 (£68).

Apple plans to deliver iOS4 to iPhone and iPod Touch users as a free update on 21 June.