Silver medallist China's Sun Yang, gold medallist Britain's James Guy and bronze medallist Germany's Paul Biedermann (L-R) celebrate after the men's 200m freestyle final at the Aquatics World Championships in Kazan, Russia, August 4, 2015. [Photo/Agencies]

KAZAN - Britain's world championships debutant James Guy beat hot favorite China's Sun Yang to win the men's 200-meter freestyle at the Kazan worlds on Tuesday.

Guy, who trailed Sun on Sunday's 400m final to finish second, won 200m in one minute 45.14 seconds. Sun was first by the 150m mark but Guy made a strong sprint in the last 25 meters to win the gold. Sun took second in 1:45.20, while Paul Biedermann of Germany, world record holder of the event, was third in 1:45.38. American veteran Ryan Lochte came fourth in 1:45.83.

"I am happy with the time," said Sun, Olympic runner-up of the event. "It is my first 200m medal in the world championships."

"It's a final with a very high level and I have never met so many strong rivals in the world championships," Sun added. "Guy surpassed me in the very last meters."

Sun, who competes four individual events at the worlds, took a sixth finish in the 800m free heats earlier Tuesday.

"I felt tired. I have been here since this morning," Sun said. "I did what my coach told me to do and I will try my best in the following competitions."

The 800m freestyle final will be held on Wednesday.

American 18-year-old swimmer Katie Ledecky broke her own world record in the women's 1500m freestyle in 15:25.48, shaving 0.23 seconds off her previous record set on Monday's heats.

Lauren Boyle of New Zealand timed 15:40.14, also an Oceanian record, to take the second. Hungary's Boglarka Kapas came third in 15:47.09.