Alex Marquez ran into the back of his brother's Ducati at the second corner. Marc Marquez lost ground but recovered to finish 1.8sec ahead of Spaniard Maverick Vinales in second with Francesco Bagnaia of Italy completing the podium.

Marc Marquez took his third Sunday victory in four race weekends this season. He has also won every sprint. His only miss came in Austin where he crashed while leading.

Marc Marquez started from pole with Alex next to him. The younger brother braked late at the second corner ramming into Marc's rear wheel.

As both lost ground, Franco Morbidelli pounced to take the lead, but did not have the pace on his Gresini Ducati to stay clear.

Vinales, on a KTM, worked his way through the pack and took the lead while Bagnaia closed in on Marc Marquez.

With seven laps to go Marc Marquez swept past Vinales and then pulled away.

"I told you before the race, I need to manage the tyres," said Marc Marquez at the finish.

"For that reason, in the first part of the race I was quiet. When Pecco (Bagnaia) came up to me I thought 'right, let's start to race'."

"Vinales was surprising. He had pace. But I had this margin at the end," said the winner

Alex Marquez lost a bit of his bike in his collision and incurred a long-lap penalty. After finishing second in every previous outing this season, he came home seventh on Sunday.

Reigning champion Jorge Martin, racing this weekend for the first time after a couple of bone-breaking pre-season crashes and still troubled by his left hand, slid out with eight laps to go and knelt in the gravel head bowed.