The first medal event to finish at the new 35,000-seater National Athletics Centre was the women's 10,000m, which finished in an Ethiopian one-two-three after Olympic champion Sifan Hassan fell having led in the closing stages.

Hassan had been content to race at the back of the lead group until the final lap, and appeared to have timed her move to perfection when she led on the final straight.

As she attempted to hold off reigning 5,000m world champion Gudaf Tsegay, Hassan fell and this season's world leader took gold in 31min 27.18sec.

"I am keeping my smile but it is really hard," Hassan said.

"I am very disappointed.

"This is sport, these things happen.

"I just had a bad moment.

"I felt really strong and tried to push in the last lap.

"I think I got pushed by the Ethiopian.

"I hope I am not crazy, I will need to look at the replay to see what exactly happened."

Defending champion Letesenbet Gidey came through in second with a season's best in 31:28.16, and Ejgayehu Taye completed a podium sweep for her country in 31:28.31.

It was unfortunate ending to the race for the Dutch, and they suffered a double misfortune when the same fate struck Femke Bol in the mixed 4x400m relay.

Liemarvin Bonevacia, Lieke Klaver and Isaya Klein Ikkink gave The Netherlands a slender lead over the United States and Britain going into the anchor leg taken by Bol.

The European champion looked set to hold off Alexis Holmes in the final stages of the relay but unbelievably fell and dropped the baton, meaning the Dutch crashed out.

"I do not know what happened," Bol said.

"It has never happened to me before.

"I cramped towards the finish line, I was pushing, pushing, pushing.

"I was disappointed that my body did not have it in to finish the race strongly."

Holmes was able to bring home a world record time of 3:08.80 after a superb display from her and team-mates Justin Robinson, Rosey Effiong and Matthew Boling.

Britain's Lewis Davey, Laviai Nielsen, Rio Mitcham and Yemi Mary John took silver in 3:11.06, and the Czech Republic were surprise beneficiaries of what unfolded at the front of the race as Matěj Krsek, Tereza Petržilková, Patrik Šorm and Lada Vondrová earned bronze in 3:11.98.

The relay provided a second gold of the day for the US, after back-to-back Olympic champion Ryan Crouser defended his men's shot put title with a Championships record.

Crouser had already broken his own record with 22.98m on his second attempt and added more than half-a-metre to it with a huge 23.51m on his final throw.

He explained the challenges he had to overcome to clinch another gold.

"The last throw was testament to all the hard work and dedication over the last year," Crouser said.

"The last few days have been hard, so it with all that has happened it was a phenomenal throw.

"It's been the most stressful 20 days I've ever had.

"The week before I was supposed to leave I woke up with calf pain and we thought I had a partial tear in my calf.

"We treated it like that but after 10 days of no improvement we had a doctor look at it and he said you have two blood clots.

"My training camp was scrapped so I had to find a way to get here.

"Luckily I had a great medical team working with me and they got me safe to fly."

A personal best of 22.34m from Leonardo Fabbri earned the Italian athlete silver, with bronze going to two-time world champion Joe Kovacs of the US with 22.12m.

In the heptathlon, the US' Anna Hall leads the way after four events with a 3,998 points tally.

The 2019 world champion Katarina Johnson-Thompson of Britain climbed to second on 3,905 with a 23.48 200m effort, and Chari Hawkins of the US is third on 3,900.

In today's heats, some of the leading names survived huge scares to progress.

Kenya's former world champion and Olympic silver medallist Timothy Cheruiyot held on to the sixth and final qualifying place in his men's 1500m heat, and Olympic champion progressed to the men's 100m semi-finals in third place with a time of 10.15 in his heat.

The second day of the World Athletics Championships tomorrow is due to feature medals in the women's 20 kilometres race walk, women's long jump, men's hammer throw, heptathlon, men's 10,000m and men's 100m.