Nokia’s planned update to its mobile phone operating system – which has been nicknamed Carla – has had some of its features revealed thanks to images leaked online.

Perhaps the biggest change can be seen on the lock screen, which has dispensed with the usual Unlock button in favour of a swipe system.

The OS also sports a new on-screen qwerty keyboard, which borrows some of its style from the Windows Phone 7 keypad that features on phones such as the Nokia Lumia.

User interfaces also appear to have been tweaked for both the music player and the web browser.

Meanwhile, a report at Nokiapoweruser claims that Nokia Carla “will have major improvements, NFC, Dolby surround; new improved widgets, improved browser (Version 8).”

Nokia handsets such as the 603, 700 and 701 are expected to ship with the OS sometime between July and September this year, while other devices such as the N8, C7, E7, X7, E6 and C6-01 will be able to upgrade by the end of 2012.

Carla is the third version of the Symbian 3 operating system, following Anna (first generation) and Belle (second gen).