Britain's Adam Peaty broke his own world record in the men's 100m breaststroke at the Rio Olympics on Saturday.

The 21-year-old clocked 57.55 seconds in the heats to shave 0.37 seconds off his record set in London last year.

"Going down that first 50, I knew it was fast, and I knew I turned fast," Peaty told reporters. "It wasn't until 25 metres to go, the crowd started to roar and it was like, there are no Brazilians in this race and they've got to be shouting for something."

Peaty, who is world champion in the event, is aiming to become the first Briton to win an Olympic swimming gold medal for 28 years.

Japan's Yasuhiro Koseki was second fastest in the heats with a time of 58.91 seconds and Brazil's Felipe Franca was third, a tenth of a second further back.