France's Leon Marchand powered to his second gold medal of the Olympics on Wednesday, producing a sensational late charge to clinch the men's 200m butterfly crown, while Swedish sprint star Sarah Sjoestroem triumphed in the women's 100m freestyle event.

World record holder and defending champion Kristof Milak of Hungary led until the final stretch when Marchand, who already has gold from the 400m medley, made his dramatic surge, roared on by the home crowd.

Marchand, who will also go for gold later on Wednesday in the 200m breaststroke, finished with a new Olympic record time of 1min 51.21sec.

Milak, who made a superb start and looked to be dominating the race, was unable to hold off the Frenchman and finished 0.54 seconds behind to collect silver while Canada's Ilya Kharun claimed the bronze.

Marchand, whose parents were both Olympic swimmers, received a rapturous reception from a crowd waving French flags and his hero status will only be enhanced by this latest performance.

The 22-year-old's win in the 400m individual medley on Sunday had given the country their first swimming gold since 2012.

Marchand is trained by Michael Phelps' former coach Bob Bowman.

Sjoestroem wins by a fingertip

Veteran Swedish sprint star Sarah Sjoestroem won the women's 100m freestyle gold medal on Wednesday, touching first ahead of American Torri Huske.

The world record holder hit the wall in 52.16secs with Huske picking up silver in 52.29 and Hong Kong's Siobhan Haughey taking bronze in 52.33.

Australia's Mollie O'Callaghan, the 200m champion, came fourth.

Huske went out hard and turned in the lead at halfway.

O'Callaghan is renowned as a fast finisher and was seen as favourite, but she failed to bring it home with Sjoestroem winning by a fingertip.

The Swede, 30, initially wasn't planning to enter the 100m.

Despite winning four Olympic medals and 25 at world championships, she had never a gold in the 100m until now.

Sjoestroem will also race the 50m freestyle.