TOKYO (Reuters) - Peruth Chemutai became the first Ugandan woman to win an Olympic gold medal in any sport when she triumphed in the women's 3,000m steeplechase on Wednesday (Aug 4).

The 22-year-old clocked a time of 9min 1.45sec to finish over three seconds ahead of American silver medallist Courtney Frerichs with Kenya's Hyvin Kiyeng taking the bronze.

"I'm so happy and proud of myself. It was a good race - I enjoyed myself and I enjoyed the weather," Chemutai said, referring to the heat in Tokyo.

Chemutai's triumph was only the third Olympic gold won by Uganda in any sport - after John Akii-Bua's 400m hurdles win in 1972 and Stephen Kiprotich's victory in the 2012 marathon.

She moved in front early in the race before Frerichs took the initiative with three laps to go, pulling away from the field.

But Chemutai responded to the challenge and overtook the American on the last lap before crossing the line 3.34 seconds ahead of her.

Kenyan world record holder Beatrice Chepkoech finished seventh, leaving her country still without a gold medal in the women's event.

Kenyans have dominated the Olympic men's 3,000m steeplechase, winning nine gold medals in a row before losing their crown to Moroccan Soufiane El Bakkali in Tokyo.

Chepkoech said she was far from at her best physically.

"I have an injury and it was so tight. I didn't even react, it's painful," she said.

"My aim was to win the race, but because of the injury, my mind was not here. It was so painful.

"I have problems with two tendons and a hamstring, low back and the stomach. I got injured before our trials in Kenya and it has been so tight since, I tried to nurse it, but it couldn't respond," she added.

Frerichs became the second American woman to win an Olympic steeplechase medal after Emma Coburn claimed bronze in Rio in 2016. Coburn fell with two laps left and finished 14th before being disqualified.

Bronze medallist Kiyeng had won silver in Rio.

While there was joy for Chemutai, it was a miserable day for heptathlon world champion Katarina Johnson-Thompson, whose Olympic bid ended abruptly when she collapsed to the track during the 200m, months after she suffered an Achilles tendon injury.

The Briton won her hurdles heat and cleared 1.86m in the high jump before pulling up in the fourth event, crumpling to the ground and grasping her right ankle as volunteers offered her a wheelchair to take her off the track.

Johnson-Thompson waved them away, bravely rising to her feet and hobbling to the finish line as the few onlookers inside the Olympic Stadium applauded her.

The Netherlands' Anouk Vetter led through the first day of competition, with Belgium's Noor Vidts second in the standings and her compatriot, defending Olympic champion Nafissatou Thiam, third.

The heptathlon will resume on Thursday, beginning with the long jump.