The images were revealed by Chinese website mobile-dad along with the alleged specs for the forthcoming device.
With a 1080p screen, the Chinese smartphone maker could opt to forgo QHD in favour of better specs elsewhere – if the information is accurate.
Qualcomm's latest Snapdragon 820 processor is expected to be included and it also looks as though the handset will feature a forward-facing speaker.
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The images also appear to show that OnePlus will do away with the fingerprint scanner, previously used on the front of the OnePlus 2.
This could point to an alternative log-in method such as iris recognition being used – we're already expecting the LG G5 to adopt such technology.
There are no further specs included in the leak, but the images suggest that there may be two versions of the OnePlus 3 available when it eventually launches.
One is the classic black, while the other appears to have some sort of mirrored finish.
The OnePlus X has not long been announced and – with the arrival of the OnePlus 2 only a few short months ago – this leak provides an unprecedented early look at the Chinese manufacturer’s next smartphone.
There is no word on when the phone will appear, but other smartphone releases – such as the Samsung Galaxy S7 – are seemingly scheduled for early next year, which could be a likely launch window for the next OnePlus handset.