ANTWERP - China's Huang Huidan claimed the title of the women's uneven bars in her first appearance at a major competition at the World Championships here on Saturday.

Huang scored 15.400 points to beat American Kyla Ross (15.266) and Russia's Aliya Mustafina (15.033), the reigning Olympic champion, and world champion in the event in 2010.

The 17-year-old national bronze medalist fought off great pressure after teammate Yao Zhennan, the first to compete, fell off the apparatus. Yao had topped the qualifying round and the all-around final on Friday.

Yao was the hot favorite to capture the gold as she became the first woman in more than 15 years to complete a "Mo Salto" on Friday, a front flip over the high bar.

But she failed to catch the bar when trying to finish the Gaylord salto again, finishing a distant 6th.

"It's really a surprise win," said Huang. "I never expected to win the gold medal on my first attempt."

A disappointed Yao could not hold back her tears and cried in the arms of her coach Xu Jinglei. Huang's gold was the first medal from the Chinese team, who sent six men and four women to the worlds and only two of them had worlds or Olympic experiences.

Japan became the biggest winner, taking two gold medals from Kenzo Shirai on the floor and Kohei Kameyama on the pommel horse.

Brazil's Arthur Nabarrete Zanetti, the Olympic champion, took the men's rings gold. Russia's aleksandr Balandin won the silver and American Brandon Wynn the bronze.

In the women's vault, defending vault champion McKayla Maroney retained her world title, beating newly-crowned all-around champion and fellow American Simone Biles.

Olympic silver medallist Maroney scored 15.724 with Biles, 16, collecting 15.595 to finish second in her first senior competition and Hong Un-jong 15.483 of DPR Korea.

The men's vault, parallel bars and high bar titles will be decided on Sunday, along with the women's beam and floor events.