The new Mercedes-AMG sedan, tipped by some to be branded as the GT4, has been spied again. This time, though, the spy photographers managed to snag some pictures of the car's interior.

The interior doesn't hold any great surprises as it features many of the design elements used in coupes and convertibles from the Mercedes-Benz stable, including four round air vents in the centre of the dashboard.

Despite its sporting nature, the GT4 will be fitted with two large high-resolution screens, as is the norm throughout most of the company's most expensive models.

The exterior has the same level of camouflage as the prototype spotted back in August, with the production car looking as though it will keep all the major elements of the concept car, which was revealed at this year's Geneva motor show.

Key changes include the fitment of proper door handles and wing mirrors, and a front fascia that's a little less aggressive.

While the GT4's exterior draws a heavy link to both the GT coupe and convertible, the new fastback sedan won't use the two-door models' unique underpinnings.

Instead, the MRA platform, used underneath all of the company's rear- and all-wheel drive vehicles from C- to S-Class, will be employed instead.

Power, at least initially, is expected to come from AMG's now ubiquitous 4.0-litre twin-turbo V8 engine. A report earlier this year suggested the next-generation CLS will not offered with a V8 engine, so as to give the GT4 a bit of space to itself.

The new AMG fastback model is widely expected to make its debut in production form some time in 2018.