Microsoft plans to show off Windows Phone 8.1 at its Build developer conference in a few days and then swiftly release the software a few weeks after that, it's claimed.

Windows Phone Central reported that Microsoft recently gave partners a final build of Windows Phone 8.1 and new phones running the forthcoming mobile OS should be available on 23 April. The report didn't specify which phones - such as the Lumia 630, Lumia 930, or Samsung ATIV SE - would get Windows Phone 8.1, but it is assumed that US market devices will be among the first.

Apart from all that, new video leaks from last week revealed some upcoming features within Windows Phone 8.1. The footage showed new Start Screen backgrounds, a parallax effect when scrolling through the Start Screen, an option that allows users to wrap an image around an existing tile, and the Lumia 630 with on-screen Windows Phone 8.1 buttons.

Microsoft will unveil Windows Phone 8.1 sometime between 2 April and 4 April, when Nokia will also allegedly introduce an international version of the Lumia Icon and a 4.5-inch handset called the Lumia 630. Both Lumia handsets are expected to be the first Windows Phone 8.1 devices. Not much else is known otherwise, but stay tuned. Pocket-lint will cover all the breaking news from Build.

READ: Windows Phone 8.1 video leaks reveal new Start Screen features

Oh, and as for the Windows Phone 8.1 Developer Preview, which lets anyone with a free App Studio account and the Developer Preview app download and run the final build of Windows Phone 8.1 on their Windows Phone 8 devices, Windows Phone Central claimed it would roll out in "late April".

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