Smartphone fans have been left in a flurry after a series of photos leaked online showing what some believe could be the long-rumoured Surface Phone. The shots, published to Twitter by serial smartphone sleuth Evan Blass, show a sleek black smartphone running what appears to be a full version on Windows 10.

Alongside a collection of renders of the mysterious phone, Blass – known to the Twitterverse as @evleaks – uploaded photos that appear to show the handset being used in the wild. According to Blass, said handset is powered by a laptop-grade Intel processor.

It should be noted that Blass never once mentions the term 'Surface Phone', although that hasn't stopped excited Twitter users speculating that the device could be the fabled Windows 10 flagship. Other sources claim that the subject of the images is in fact a Dell-made mobile phone that runs a full version of Windows 10, as opposed to Windows 10 Mobile.

Tech news site Thurrott, which cites "sources familiar with the matter", goes on to report that the handset pictured was a planned Dell device based on x86 Intel architecture, that was scuppered when Intel abandoned plans for an Atom mobile chipset earlier this year.

Whatever it is, Blass suggested in a Twitter exchange with the Verge reporter Tom Warren that the phone in the pictures is "much more than a concept", and suggested users keep their eyes open for further info.

Exactly what we're looking at, then, remains a mystery. If Microsoft is planning a Surface Phone, it would likely be the company's last chance to turn around its mobile business. Windows Phone now accounts for less than one percent of the worldwide smartphone market and, with the arrival of entirely new product ranges like the Surface Studio and HoloLens, Microsoft may wish to cut its losses with mobile and instead dedicate itself to carving out a mantle for its new hardware.

Either way, Blass usually tends to be on the money when it comes to all things smartphone, so one way or another we expect to hear more about this mysterious Windows Phone in the (hopefully) not-too-distant future.