After I lifted off the accelerator pedal, the vehicle accelerated as the engine revved up quite aggressively.

I held the vehicle on the brake and stopped somewhere safe. With my foot on the brake, I bent down and checked that the accelerator pedal wasn't jammed. moving the pedal with my hand, the engine response did not change.

Even in neutral the engine revved up to 7,000 rpm.

Keying the vehicle off & on again resolved the problem, but this could have been very dangerous in different surroundings.