KAZAN: American Katie Ledecky entered the record books as she smashed the women's 800 meters world record to claim her fifth gold medal of a remarkable world championships on Saturday.

Ledecky, the 18-year-old high school graduate, blitzed her way to gold in eight minutes 7.39 seconds, setting her third world record of the week and 10th of a glittering career.

New Zealander Lauren Boyle upgraded her 2013 world bronze to claim silver, 10.26 seconds behind Ledecky, as she just held off Jaz Carlin of Britain by 0.50 seconds.

Ledecky's one-way win also saw her become the first swimmer across both genders to secure world titles over the 200m to 1500m distances.

Sun Yang of China had the same ambition, but was defeated in the men's 200m freestyle final on Monday.

Chad le Clos won his first individual title of the week as the South African smashed his personal best in winning the men's 100m butterfly.

Le Clos, unbeaten in the event since London 2012, held the lead at the turn before creating daylight between himself and Laszlo Cseh to post 50.56 seconds.

The Hungarian took silver, 0.31 seconds behind, with Joseph Schooling of Singapore setting an Asian record to claim bronze.

Emily Seebohm garnered Australia's sixth gold medal of the championships with a remarkable final lap to take the women's 200m backstroke title.

Defending champion Missy Franklin, of the United States, had led at 100m, but Seebohm timed her finale to perfection to snatch the lead in the final 25m, striking gold in 2:05.81.

The 23-year-old Australian's final split of 31.14 seconds was nearly two seconds quicker than a flagging Franklin, who gamely held on for silver.

Katinka Hosszu of Hungary took bronze.

Olympic champion Florent Manadou's sprinting prowess continued as the Frenchman took the men's 50m freestyle gold in 21.19 seconds.

Manadou had already won the men's 50m butterfly title and raw power secured him gold here, with Nathan Adrian, of the United States, taking silver in 21.52 seconds.

With Brazil's defending champion Cesar Cielo forced to return home with a shoulder injury, compatriot Bruno Fratus took up the mantle to claim bronze.

Sweden's Sarah Sjostrom powered to the women's 50m butterfly title for her second gold of the week to become the first woman to claim the world butterfly double.

A boisterous crowd of 10,000 inside the Kazan Arena roared on Russia in the mixed 4x100m freestyle relay.