PHILLIP ISLAND - Spaniard Jorge Lorenzo won a chaotic Australian MotoGP on Sunday, throwing the race for the world championship wide open as title leader Marc Marquez was disqualified at Phillip Island.

The defending world champion pulled to within 18 points of rookie Marquez at the top of the championship with two races to go after his countryman was sensationally black-flagged for ignoring a mandatory pit stop in the middle stages of the race. The MotoGP was shortened to 19 laps from a scheduled 26 laps because of safety concerns over Bridgestone tyres degrading on the new tarmac surface.

Riders were required by race officials to make a mandatory pit stop by the 10th lap of the race and change to a replacement machine to avoid potentially dangerous tyre wear. Marquez instead remained on the track on his Repsol Honda for an extra lap and incurred a black flag from race officials, disqualifying him. That enabled Lorenzo to make up a maximum 25 points and keep alive the world title race with two events of the championship remaining, at Motegi and Valencia. Marquez went into the weekend leading Lorenzo by 43 points and was poised to become the first rookie rider to clinch the premier class championship since American Kenny Roberts 35 years ago.  He is now in a fight with Lorenzo for the world crown. "Today was a crazy race and much different than a normal race with the change of bikes in the middle of the race," said Lorenzo.

"Twenty five points, the best result possible, and we now have opened the world championship, but it is still very tough. I'm really happy with this win, we've also been lucky because Marc made this mistake. Without that he would have been second or first because he was really fast today. Let's see what happens in Motegi."

Marquez, 20, admitted that he would learn from his mistake. "Today was our first experience of a flag-to-flag race, and suffice to say it wasn't a good one," Marquez said.

"My team and I had set out a strategy and we thought that we could come in after lap 10, but in reality this counts as an extra lap. We hadn't had that in mind and this was a huge mistake. We had everything well planned and I followed the instructions on my pit board. You learn from these things though, so now we have to move on and focus on the race in Japan."

Prior to Marquez's costly error, Lorenzo's Yamaha had the edge over his Repsol Honda opponent over the weekend and he powered to the first bend off the pole to take control of the race. It was Lorenzo's sixth win of the season -- the same number of wins by Marquez -- and 29th in his MotoGP career.

Lorenzo broke through for his first premier class win at the Phillip Island circuit where he had two 250cc victories in 2006 and 2007 and also sealed his world MotoGP title here last year. Marquez's Repsol Honda teammate Dani Pedrosa was second, 6.936 seconds adrift of Lorenzo, with Yamaha's seven-time premier class world champion Valentino Rossi making the podium in third place just ahead of Britain's Cal Crutchlow.