The 15-year-old sensation, who was born in Handen, first made international waves last year when she won the same event in the European long course championships in a time of 58.44.

Jessicah Schipper came second behind Sjostrom in a time of 56.23, while China's Jiao Liuyang won the bronze medal in a time of 56.86.

In the men's 100m backstroke, world record holder Aaron Peirsol was sensationally knocked out in the semi-finals when he managed no better than the ninth-fastest time, while Japan's Junya Koga swam a championship record in 52.39.

Germany's Helge Meeuw and Koga's compatriot Ryosuke Irie followed into the final.

Spain's Aschwin Wildeboer, who swam a championship record in the heats in the morning session, had the fourth-fastest time.

Soni, who swam a championship record in the heats in the women's 100m breaststroke went one better in the semi-finals, when she managed to break Leisel Jones' world record.

Jones' time was 1:05.09, which Soni bettered by. 25 seconds, thereby becoming the first swimmer to manage to get under the 1:05 mark in a time of 1:04.84.

She was followed into the finals by Russian Yuliya Efimova and Australian Sarah Katsoulis.