Australia's Cate Campbell won the women's 100m freestyle gold at the swimming world championships on Friday as US star Missy Franklin missed out on claiming a fifth medal in Barcelona.

The 21-year-old Campbell earned her first major title when she clocked 52.34sec with Sweden's Sarah Sjostrom, the 100m butterfly world champion, at 0.55 back and Olympic champion Ranomi Kromowidjojo of Holland adrift at 1.08.

Having already collected four golds in Barcelona, Franklin missed out as she finished fourth at 1.13 back, while Germany's Britta Steffen, whose 2009 world record was under threat from Campbell until the dying stages, finished sixth.

It didn't really sink in until I got out and heard all the Aussies

Cate Campbell, Australian swimmer

Having missed the event at the London Olympics after suffering from gastroenteritis during London 2012, Campbell burst into tears as she climbed out of the Palau Sant Jordi pool.

"It didn't really sink in until I got out and heard all the Aussies screaming," said Campbell, who held a clear lead before fading in the last ten metres.

"I think if the race had lasted 110 metres I wouldn't have got it."

Franklin had no time to dwell on her defeat.

Just 15 minutes after the freestyle final, the 18-year-old was back in the water as the fastest qualifier into Saturday's 100m backstroke final, her strongest event in which she is Olympic champion and world-record holder.

In other news from Spain, American Ryan Lochte won the third 200 metres backstroke gold of his career.

The decorated 28-year-old clocked a time of one minute 53.79 seconds, with Radoslaw Kawecki of Poland taking silver in 1:54.24 and Lochte's compatriot, Olympic champion Tyler Clary, bronze in 1:54.64.

Lochte, who won 200 metres individual medley gold on Thursday, is only the second man to win three 200 backstroke titles after compatriot and world record holder Aaron Peirsol, who won four in 2001, 2003, 2005 and 2009. 

Lochte was champion in 2007 and at the last world championships in Shanghai two years ago.

Source: Agencies