Armand Duplantis fulfilled a childhood dream as he broke his own pole vault world record in retaining his Olympic crown on Monday but Simone Biles showed she is human after all.

The day after US sprinter Noah Lyles blasted his way into the record books with the narrowest of wins in the men's 100m, a pulsating Stade de France witnessed another historic evening of track and field action.

Not for the first time, the night belonged to the invincible Duplantis.

The US-born Swedish great was the sole vaulter to go beyond the six-metre mark, leaving American Sam Kendricks trailing in a distant silver, with Greece's Emmanouil Karalis in bronze.

After securing gold again, it was then a case of how high the 24-year-old Duplantis could go.

He set a record of 6.24m in April but with the Stade de France holding its breath, he bettered that on his third and final attempt at 6.25m before milking the deafening applause of the crowd.

"What can I say? I just broke a world record at the Olympics, biggest possible stage for a pole vaulter," Duplantis said.

"The biggest dream since a kid was to break the world record at the Olympics and I've been able to do that in front of the most ridiculous crowd I've ever competed in front of."

Kenya's Beatrice Chebet produced a masterful display of tactical running to win the women's 5,000m and end defending champion Sifan Hassan's dream of a long-distance treble.

Britain's Keely Hodgkinson produced a thrilling gun-to-tape run to win the women's 800m while America's Valarie Allman defended her discus title.

In early action at the track, the "big three" advanced comfortably in the heats of the men's 400m hurdles, seen as one of the most competitive races of the Games.

Defending champion Karsten Warholm and his challengers, American Rai Benjamin and Brazilian Alison Dos Santos, all cruised through and eased up well before the line.

Fresh from his breathtaking triumph, Lyles breezed to victory in his 200m heat with a time of 20.19sec to reach the semi-finals.

- Biles settles for silver -
Earlier in the day, all eyes were on Biles to see if she could write some more history of her own.

Widely considered the greatest gymnast in history, the American was bidding to add to her Paris haul of three golds in balance beam and floor finals at the Bercy Arena, in her final day of competition.

But the 27-year-old slipped off the beam while walking backwards in her routine, the unusual error gifting gold to Italy's Alice D'Amato.

A furious Biles exited the arena to prepare for her floor exercise final, which also ended in heartbreak as two landing hiccups sent her into silver behind Brazil's Rebeca Andrade.

"Today has been absolutely wild," Biles said, adding that she was "actually very happy, proud and even more excited that it's over".

She famously fell victim to the debilitating mental block gymnasts call the "twisties" at the Tokyo Olympics three years ago but has bounced back emphatically to silence critics who slammed her as a quitter.

Biles ended her campaign in Paris with three golds and a silver, bringing her total Olympic haul to 11, seven of which are gold.

- 'Food poisoning' -
The River Seine was judged clean enough to stage the mixed triathlon relay following uncertainty over pollution levels and illness in the build-up.

The race turned out to be a thriller, Germany's Laura Lindemann holding off a fierce challenge from the United States and Britain to take gold.

Belgium withdrew after one of their athletes fell ill after competing in the Seine last week but officials gave the all-clear for Monday's race after assessing the water.

The Seine has been the focus of attention during the Games, consistently failing water quality tests despite a 1.4 billion euros ($1.5 billion) upgrade to improve the Paris sewerage and water treatment systems.

In a packed day 10 schedule, track cycling began at the National Velodrome.

Britain gave what they hope will be a taste of things to come by storming to the first gold, in the women's team sprint, with the world record shattered five times in the session.

In football, substitute Juanlu Sanchez struck a late winner as Spain came from behind to beat Morocco 2-1 and reach the final of the men's competition.

There they will face hosts France who defeated Egypt 3-1 after extra-time.

South Korea's An Se-young won women's badminton gold, with Denmark's Viktor Axelsen retaining his men's crown.

China top the medals table with 21 golds, one ahead of the United States.