Here are some fresh spy shots of BMW’s new Mercedes CLS and Audi A7 Sportback adversary, the four-door version of the latest 6-Series, which was spotted testing in Europe.

The third iteration of the 6-Series after the two-door Coupe and Convertible models will most likely be called the 6-Series GT or the 6-Series Gran Coupé and will reach showrooms in the first half of 2012. BMW believes the four door model will overshadow the rest of the range and predicts that it will account for around half of all 6-Series sales.

Our latest scoop shows the sporty BMW sedan finished in a black color, which makes it look more elegant and sinister than the previous white prototype we showed you a couple of weeks ago.

The four-door 6er will be offered with a similar engine lineup to the Coupe and Convertible models including a 3.0-liter straight-six turbocharged petrol with 320-horses for the 640i, a 4.4-liter turbo V8 with 407HP for the 650i and a 3.0-liter turbo diesel with 313-horsepower for the 640d.

Given the recent announcement on the all-wheel drive variants of the 6-Series Coupe, it’s a fair possibility that BMW will offer the GT with its xDrive system as well.

A hot M6 variant equipped with the new M5’s 4.4-liter twin-turbocharged V8 delivering around 560-ponies is also expected down the line.

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