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(Pocket-lint) - Microsoft is due to unveil a couple of handsets during its Mobile World Congress press event tomorrow, Monday 2 March. However, the company has already mistakenly spilled the beans on what to expect.

It accidentally posted an article on its online "news center" site that, while blank, had a headline that gave the game away; it will be announcing two Windows Phone handsets, the Lumia 640 and a presumably larger version in the 640 XL.

We don't actually know much else about the devices, at least officially, so there's still plenty for Microsoft to unveil during the event, but we suspect it might only be focusing on the low-to-mid level at this year's trade show.

Previous rumours have suggested that the Lumia 640 will be a 5-inch phone with a Qualcomm Snapdragon 400 processor, 1GB of RAM and 8GB of on board storage.

The leak also said that it would have an 8-megapixel camera on the rear and a 1-megapixel camera on the front. It is presumed that the XL version of the 640 will have a larger screen at the very least - but could be similar in other spec.

We'll know for sure when the Microsoft event starts at 7.30am GMT tomorrow morning.

Writing by Rik Henderson.