The third-generation BMW X4 is in the works as a coupé-roofed version of the new iX3 EV, set to offer a range of more than 500 miles per charge.

Prototypes of the new SUV have been spotted testing for the first time ahead of its unveiling, expected to take place early next year.

It will be the first X4 to offer an electric powertrain, the model having only offered petrol and diesel options since it was first launched in 2014.

Being based on the iX3, it shares many of its visual cues with that car, but it gains a more steeply raked roofline.

This is likely to compromise head room in the second row but, given its more streamline shape, will also bring a small boost to the range of the EV.

That could make the iX4 the longest-range EV sold in the UK, given the current iX3 holds that title with the ability to drive 500 miles between charges. However, the smaller and sleeker BMW i3 saloon – based on the same underpinnings and also due next year – could gazump the iX4.

Mechanically, the iX4 is likely to offer the same mix of motor configurations as the iX3. The flagship 50 xDrive employs a synchronous motor on each axle, combining for outputs of 464bhp and 479lb ft. That enables the SUV to complete the 0-62mph dash in a claimed 4.9sec.

The iX3’s 800V electrical architecture also allows it to charge at rates up to 400kW, and this is likely to be mirrored by the iX4.

Inside, it will adopt BMW’s new panoramic iDrive system, bringing a 17.9in infotainment touchscreen that is positioned below a thin driver information display which spans the width of the windscreen.

Production of the current X4, which went on sale seven years ago, is earmarked to end in the coming weeks.