World record holder Van Niekerk was the overwhelming favourite after Botswana's Isaac Makwala was ruled out of the event and was never really challenged during the final.

After running a sublime final bend, the 25-year-old eased off the pace in the closing stages to finish in 43.98s, significantly slower than the 43.03s he set during the Olympic Games in Rio de Janeiro in 2016, but well ahead of his rivals on the day.

Steven Gardiner of the Bahamas was a distant second in 44.41s, while Sudanese-born Qatari Abdalelah Haroun (44.48s) completed the podium.

"It's an amazing blessing," Van Niekerk told the media after the race.

"I've got a good team that will help me recover after this and I'll be back tomorrow."

Van Niekerk next takes part in the 200m semi-final on Wednesday, where he is favourite to triumph as well following Makwala's withdrawal.

Should the South African be successful, he will be the first athlete since Michael Johnson in Gothenburg in 1995 to win the 200m/400m double at the World Championships, a feat the American also managed at the Olympics the following year.