Dana Vollmer of the United States won the first gold medal for her country at the Shanghai worlds as the 23-year-old claimed the women's 100m butterfly title on Monday.

Vollmer, runner-up of the event at the 2009 Rome worlds, pulled away over the last lap to win the gold in 56.87 seconds, while Aussie Alicia Coutts took the silver in 56.94. Lu Ying of China delighted the home crowd with a bronze at 57.06.

The 22-year-old Lu, bronze medallist of the event at the Asian Games last November, was satisfied with her World Championships debut.

"I just expected a top eight before the final," she said. "So I didn't feel much pressure."

"The key to my good result is advanced training regime and the coach's help," added Lu, who used to be a freestyle specialist but changed to butterfly in 2008.

Defending champion and world record holder Sarah Sjoestroem of Sweden managed a fourth finish in 57.38. Olympic women's 200m fly champion Liu Zige of China took the sixth in 57.57.

"I will try my best in all the events," said the 22-year-old Liu. "I hope I can achieve better results in the following events."

Another Aussie Jessicah Schipper, 200m butterfly winner at the 2009 Rome worlds, finished seventh in 59.95.