Sydney McLaughlin obliterated her own world record to win Olympic gold in the women's 400m hurdles on Wednesday as Japan's Sakura Yosozumi maintained the hosts' stranglehold on the skateboarding competition.

Elsewhere on day 12 of action in Tokyo, the Netherlands dumped defending champions Britain out of the women's hockey while the women's golf got under way.

At the Olympic Stadium, McLaughlin powered home under the beating Tokyo sun in 51.46 seconds, with defending champion Dalilah Muhammad claiming silver in 51.58 after another classic duel between the two dominant American hurdlers.

World champion Muhammad made a flying start in the lane outside her compatriot and rival but McLaughlin produced a late burst of speed to claim victory.

Sky Brown (L) is the reigning X Games champion Sky Brown (L) is the reigning X Games champion Photo: GETTY IMAGES NORTH AMERICA / Sean M. Haffey

The 21-year-old McLaughlin's blistering time bettered her world record set at the US trials in Oregon in June, when she ran 51.90sec.

Muhammad, 31, also ducked inside the previous world record, with bronze medallist Femke Bol of the Netherlands just outside the 52-second mark.

It came a day after an epic duel between Karsten Warholm and Rai Benjamin in the men's 400m hurdles, which ended with Norway's Warholm winning and improving his own world record by a huge margin.

"What a great race," said McLaughlin. "I'm just grateful to be out here celebrating that extraordinary race and representing my country.

Sydney McLaughlin wins the women's 400m hurdles gold at the Tokyo Olympics Sydney McLaughlin wins the women's 400m hurdles gold at the Tokyo Olympics Photo: AFP / Jewel SAMAD

"I saw Dalilah ahead of me with one to go. I just thought 'run your race'. The race doesn't really start till hurdle seven. I just wanted to go out there and give it everything I had."

Canada's Damian Warner leads the way in the men's decathlon after three events while defending champion Nafi Thiam of Belgium tops the heptathlon standings with two events gone. British world champion Katarina Johnson-Thompson is in third spot.

In a hotly anticipated men's 200m final in the evening session, pre-Games favourite Noah Lyles takes on exciting 17-year-old US compatriot Erriyon Knighton and Rio 2016 silver medallist Andre de Grasse.

Canadian De Grasse was the fastest man in the semi-finals with a national record 19.73, 0.1sec quicker than another American, Kenneth Bednarek.

Sydney McLaughlin (right) beat US rival Dalilah Muhammad in the final of the women's 400m hurdles, setting a new world record Sydney McLaughlin (right) beat US rival Dalilah Muhammad in the final of the women's 400m hurdles, setting a new world record Photo: AFP / Javier SORIANO

Dutch star Sifan Hassan will be also be attempting the next step in her bid for an unprecedented treble, running in the 1500m semi-finals two days after winning the 5,000 title.

Away from the athletics, Yosozumi won the women's park skateboarding event to stop compatriot Kokona Hiraki and Britain's Sky Brown becoming the Games' youngest-ever gold medallists.

The 19-year-old carved up the Ariake Urban Sports Park with a flowing opening run in the final, and her 60.09 points proved enough for victory ahead of Hiraki and Brown.

Brown threatened to snatch a shock win with a flawless closing routine but her 56.47 was not enough.

Japan also snapped up the men's and women's street titles earlier in the Games and they have now bagged five of the nine medals so far as skateboarding makes its debut as one of four new Olympic sports.

Both Brown, at 13 years and 28 days, and Hiraki (12 years and 343 days) were bidding to break an 85-year-old record to become the youngest Olympic gold medallists.

In early action in Tokyo, Marcela Ana Cunha of Brazil held off a charge from defending champion Sharon van Rouwendaal of the Netherlands to win the women's 10-kilometre marathon swimming event.

The Dutch team hammered Britain 5-1 in the semi-finals of the women's hockey while Serbia edged China 77-70 in their women's basketball quarter-final to set up a last-four clash against either Australia or the USA.

World number one women's golfer Nelly Korda was the early clubhouse leader after completing her first round at the Kasumigaseki Country Club in a four-under-par 67.

China continued their march towards another table tennis team gold, crushing Germany 3-0 to set up a mouth-watering final against Japan.