Marquez, who was flipped off his bike after it hit a wall, was removed from the track in an ambulance and taken to hospital.
His bike was destroyed while other riders including Raul Fernandez and Fabio Di Giannantonio were also involved.
The race's medical services said all riders were conscious after the crash, which appeared to be started by Pedro Acosta's bike cutting out.
The grand prix will be restarted for 13 laps with grid positions based on standings as of lap 11.