Japan celebrates gold rush on day of upsets at Olympics

A Japanese skateboarder claimed a piece of Olympic history as the host nation enjoyed a gold rush on a day of upsets at the Tokyo Games on Sunday.

The second full day of competition saw 18 gold medals up for grabs, including the first ever in skateboarding, one of several new sports introduced in Tokyo as part of an International Olympic Committee drive to attract younger fans.

A perfectly scripted final saw Japanese world champion Yuto Horigome strike gold in a tense street competition.

The 22-year-old, who grew up just a stone's throw from the Olympic venue, landed three huge tricks in a row to eclipse American favourite Nyjah Huston, who finished seventh.

"This is special because it was held in Koto City, where I was born," said Horigome. "For me it's very meaningful, very inspiring."

Horigome's victory was one of four golds snaffled by Japan on Sunday.

The haul included a remarkable judo double, with brother and sister Uta and Hifumi Abe both winning Olympic titles within an hour of each other.

Uta Abe was first to strike gold in the women's under-52kg category, beating Amandine Buchard of France in the final.

She then cheered on as her big brother Hifumi overpowered Georgian judoka Vazha Margvelashvili in the under-66kg gold medal fight.

Earlier, unheralded swimmer Yui Ohashi had sparked the Japan gold spree in an action-packed morning finals session at the Tokyo Aquatics Center.

Ohashi powered to victory in the women's 400 individual medley, toppling Hungary's defending champion Katinka Hosszu.

Ohashi -- whose previous best performance on the world stage was a silver medal at the 2017 World Championships -- touched in 4:32.08 ahead of US duo Emma Weyant and Hali Flickinger.

"I swam believing in myself. I really did not think of winning the gold," said Ohashi.

Cycling, tennis upsets

Ohashi's win was upstaged however by Tunisian teenager Ahmed Hafnaoui, who pulled off a massive shock in the men's 400m freestyle to take gold.

The 18-year-old had only qualified eighth-fastest for the final but produced a devastating late burst to win in 3min 43.36sec, overhauling Australian Jack McLoughlin, who took silver in 3:43.52.

"I just can't believe that, it's amazing," Hafnaoui said. "I felt better in the water this morning than yesterday and that's it. I'm the Olympic champion now."

It was Tunisia's first ever Olympic medal in the event and just their third gold ever in swimming.

The other swimming medals were split between the US and Australia, with Chase Kalisz winning the 400m medley and Australia taking gold in the women's 4x100m freestyle relay in a world record time of 3:29.69.

The upsets extended beyond the pool later Sunday, with Australian world number one Ashleigh Barty crashing out in the first round of the women's tennis singles. Barty, the reigning Wimbledon champion, lost 6-4, 6-3 to Spain's Sara Sorribes Tormo.

Austrian mathematician Anna Kiesenhofer meanwhile claimed a shock victory in the women's cycling road race, which ended in bizarre fashion with Dutch veteran Annemiek van Vleuten crossing the line mistakenly thinking she had won.

Van Vleuten punched the air as she finished, oblivious to the fact that Kiesenhofer had broken away from the peloton earlier to take gold.

"Yes, I thought I had won," van Vleuten said. "I'm gutted about this, of course. At first I felt really stupid, but then the others (her teammates) also did not know who had won."

Golf chaos, Biles wobbles

Elsewhere on Sunday, a century-long wait to see surfing at the Olympics came to an end at Tsurigasaki Surfing Beach.

Blue skies and blazing sunshine greeted surfers as they paddled into the Pacific Ocean for the men's and women's heats.

It marked the culmination of efforts to get surfing added to the Olympic programme which date back more than 100 years.

The spectre of Covid-19 meanwhile continued to stalk the Olympics, with the men's golf tournament upended by two high-profile withdrawals.

World number one Jon Rahm was ruled out after returning a positive test -- his second Covid-19 positive in two months -- while Bryson DeChambeau also saw his Olympic hopes end with a positive case.

In gymnastics, US superstar and defending champion Simone Biles produced a rusty performance in qualifying, with several uncharacteristic mistakes in a near-empty arena.

Biles rolled her eyes after one unsteady landing on the vault and had her performance director Tom Forster shaking his head in disbelief after a shaky end to her beam routine.

"Simone took three big steps on the beam dismount, I've never seen her do that before," said Forster.

"We're going to be okay... this is not the finals, this is getting into the finals, this might be a great awakening for us," he said.

—Agence France-Presse