Sweden's Sarah Sjostrom has smashed her own world record in the 100m butterfly final to secure gold at the World Championships in Kazan, Russia.

The 21-year-old, who first broke the record in the semi-finals on Sunday, lowered her time by a hundredth of a second to touch the wall in 55.64s on Monday.

Denmark's Jeanette Ottesen finished the race in 57.05s to claim silver, while Lu Ying of China rounded off the podium in a time of 57.48s.

Sjostrom won the title in Barcelona two years ago.