HTC First 'Facebook phone' leaked?

Facebook's rumoured new smartphone may have been leaked on Twitter just days before it is expected to be unveiled.

An image of what appears to be a device called the 'HTC First' has been published by Twitter account @evleaks.

The image shows no HTC branding on the phone. The device appears to have Android's traditional three capacitive buttons below the screen, but the home button indicator is a hollow circle.

Facebook has scheduled a press event later this week where the company is widely expected to unveil a smartphone built entirely around the social network.

The image comes just a day after US blog Android Police published details of what appeared to be a leaked version of a Facebook OS.

The HTC First is expected to be a mid-range device. It is likely to come with a dual-core processor and a 5-megapixel camera and will run the Android 4.1.2 Jelly Bean operating system.