Nigeria's Tobi Amusan set a new 100m hurdles world record as the event's semi-finals delivered an extraordinary set of times.

The 25-year-old, who ran a new African record of 12.40 seconds in Saturday's heats, clocked 12.12 seconds.

Her time beat the 12.20 seconds set by American Kendra Harrison, who finished second behind Amusan, in 2016.

"I wanted to get out and go," said Amusan. "I did what I had to do."

Amusan went on to win gold in the final, two hours later.

Great Britain's Cindy Sember finished fourth in the semi-final won by Amusan but qualified for the final with a new British record of 12.50, beating sister Tiffany Porter's 2014 mark by one hundredth of a second.

It was one of four national records, excluding Amusan, run in the semi-finals with another seven athletes equalling or breaking their personal bests.

"That was a crazy race. I actually thought I was running slow. Tobi was amazing, I can't deny," said Sember. (Text, excluding headline: BBC)