After four drivers, headed by BMW's Marco Wittmann, stopped on the opening lap and caught up to the back of the field during a safety car stoppage, Muller kept the quartet at bay for much of the race, leaving his own mandatory stop late.

He was ahead of the four when the group cycled to the front with Audi's Mattias Ekstrom emerging out of the pits almost 20 seconds behind the quartet.

As Muller controlled the pace out front, Ekstrom and the rest of the pack closed in on the group. Muller eventually pitted on lap 33 of 36, releasing the early-stopping Maro Engel to go on and take the win - but Ekstrom only missed out on first place by 0.3s in second.

Muller eventually pitted on lap 33 of 36, releasing the early-stopping Maro Engel to go on and take the win - but Ekstrom only missed out on first place by 0.3s.

After the race, Muller's conduct and strategy were questioned by Mercedes and BMW.

BMW motorsport boss Jens Marquardt told Motorsport.com: "Nico Muller was doing nothing but blocking and trying to do - in bike racing, you say, Wasserträger [water carrier] for the big boss - and this he did well.

"I have to say, for me, this is not the kind of racing we really want to see, this is nothing for the fans.

"Clearly, you have to say, you want to show races for the fans and what fans want to see are proper straight fights, head to head and not strategy and chess-playing with cars.

"To me, this is really not what people want to see, what they come out for and what they paid money for - but that's for somebody else to decide. We fight hard, we race hard, that's what we did today, that's the best we could do today."

His sentiments were echoed by Mercedes DTM boss Ulrich Fritz, who told Motorsport.com: "I mean, we have to ask the question if we want to play chess or if we want to go racing.

"In the end, what I saw from Mr. Muller was intentionally holding back the guys behind.

"Maro was lucky and could win the race but especially the guys at BMW [Wittmann and Tom Blomqvist] lost a lot of places by that - and the same thing could've happened to us. I don't really get it, I have to say."

Wittmann: Audi tactics "unacceptable"

Reigning champion Wittmann, who led the early-stopping drivers during the safety car, felt his race was "destroyed" by Muller - as he used up his allocated DRS activations while trying to pass, and was overtaken by Engel and eventually ended up only sixth.

"Audi left Muller staying out until nearly the end of the race and slowing us down, me, Maro and so on, quite massively," Wittmann told Motorsport.com.

"It was quite obvious what he did, slowing us down in the high-speed, medium-speed corners, he tried to make a gap just before the straight not to get passed and then slowing us down by two seconds per lap.

"For me, that has nothing to do with fair racing, to be honest. For me, it's a bit unacceptable what they do. They should just go, race and maybe win the race if they are better or quicker but not destroying the race of other drivers.

"I am quite disappointed because today we maybe could've won and they actually destroyed my race."