The next-generation BMW M3 sedan has been spied during testing on public roads in Europe.Compared to earlier prototypes, this latest car has no false panels covering the headlights. Rather than using the notched units present on the 3 Series sedan and wagon, the M3's seem awfully similar to ones spied on 4 Series prototypes.In a leaked photo, the new 4 Series sports a tall and narrow double-kidney grille, like the one on the Concept 4 coupe at the Frankfurt motor show.Although there's still plenty of disguise around the car's air intakes, it's possible both the M3 and M4 will share the controversial 328-inspired grille.Today's prototype also features the line's signature wing mirrors, and four snarling exhaust tips poking out of the rear bumper. Mind you, we've already seen the car's rear-end design completely undisguised thanks to a leak in October.Last month Markus Flasch, head of the BMW M division, confirmed the M3 and M4 won't go on sale globally until 2021.The new high-performance sedan and two-door models will be available with a manual transmission, as well as rear- and all-wheel drive variants.Details about the powertrain have yet to be revealed, but Flasch promised they "will have the most powerful engine in the segment".Power is believed to come from the 'S58' 3.0-litre turbocharged six-cylinder family used in the X3 M and X4 M, both of which top out with 375kW of power and 600Nm of torque.By way of comparison the Alfa Romeo Giulia Quadrifoglio has 375kW/600Nm from its 2.9-litre V6, while the Mercedes-AMG C63 S boasts 375kW/700Nm from its 4.0-litre twin-turbo V8.MORE: M3 news, reviews, comparisons and videosMORE: Everything BMW

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