PHILLIP ISLAND, Australia (AFP) - Spaniard Jorge Lorenzo kept alive the race for the world championship with victory in a controversial Australian MotoGP at Phillip Island on Sunday.

The Yamaha rider pulled to within 18 points of Marc Marquez at the top of the championship with two races left after Marquez was sensationally black-flagged for ignoring a mandatory pit stop in the middle stages of the race.

The Australian MotoGP was shortened to 19 laps from a scheduled 26 laps amid safety concerns over Bridgestone tyres degrading on the new tarmac surface on the Phillip Island track.

Riders were required to make a mandatory pit stop by the 10th lap of the race and change to a replacement machine.

But Marquez instead stayed on the track on his Repsol Honda for an extra lap and incurred a black flag from race officials. He was forced to re-pit, where he left the race.

That enabled Lorenzo to make up a maximum 25 points and keep alive the world title race.

Marquez had led Lorenzo by 43 points coming into the Phillip Island race and would have become the youngest-ever MotoGP champion if he had managed to outscore Lorenzo by eight points.

Marquez's Repsol Honda team-mate Dani Pedrosa was second, 6.936sec adrift of Lorenzo, with Yamaha's Valentino Rossi making the podium in third place.

The two races to come are at Motegi and Valencia.

Rider standings:

1) Marc Marquez (Spain) Honda 298.

2) Jorge Lorenzo (Spain) Yamaha 280.

3) Dani Pedrosa (Spain) Honda 264.

4) Valentino Rossi (Italy) Yamaha 214.

5) Cal Crutchlow (Britain) Yamaha 179