LONDON: Romania's Sandra Izbasa upset American favorite McKayla Maroney to strike gold in the women's gymnastics vault final at the Olympics on Sunday.

Maroney had been expected to run away with the gold after she topped qualifying with her near-flawless 2-1/2 twisting Amanar somersault.

After incurring a penalty for stepping out of bounds on her signature vault, the American teenager then looked shell-shocked as she sat down following her second vault, a half-on-straight with full twist.

Despite the mishap, the high difficulty levels of her somersaults had her top of the pile until Izbasa, the final competitor, leapfrogged her with two relatively clean, if not spectacular leaps.

Izbasa earned an average of 15.191 while Maroney was awarded 15.083.

Russia's Maria Paseka picked up the bronze.