Spied: Jaguar's upcoming 3-Series fighter

Jaguar is taking square aim at cars like the 3-Series, C-Class and A4.

Jaguar's BMW 3-Series-fighter has officially moved out of the rumor mill and into the real world. After a lengthy buildup, our spy photographers have sent us the first images proving Jaguar's compact sedan program is well underway.

Don't let this test mule's body work fool you - beneath that XF exterior resides a new compact sports sedan that will take on vehicles like the BMW 3-Series, Mercedes-Benz C-Class and Audi A4.

A closer inspection reveals the donor XF's roof, doors and decklid have been altered to fit the compact footprint of the smaller sedan, internally known as the X760. Although we can't comment of the car's styling at this point, Jaguar's recent F-Type sports car should be a good indication of what to expect from the company's 3-Series fighter.

The compact sedan, which could be branded as the XS, is expected to ride on a version of the same Premium Lightweight Architecture that underpins the Jaguar XJ. That means the XS should not only be among the lightest vehicles in its class, but also be available with rear- and all-wheel drive.

As far as engines go, we hear the XS will arrive with a turbocharged four-cylinder as its base engine, with Jaguar's new supercharged V6 also on offer. A hotter XS-R model is likely, but it remains unknown which mill might power that car.

Look for the Jaguar XS to hit the market sometime in 2015, possibly as a 2016 model.