World champion Dafne Schippers was involved in a bizarre women's 200 metres at the Oslo Diamond League meeting on Thursday when the Dutchwoman false-started, was allowed to race and won, was then disqualified and finally reinstated.

Canadian Olympic bronze medallist Andre De Grasse had a far more straightforward victory as he edged home to win the 100 metres with his best time of the season.

Britain's Jake Wightman pulled off a shock win in the men's 1500 metres and Olympic champion Kerron Clement came in last in the men's 400 metres hurdles, won by Norwegian Karsten Warholm.

But all the drama surrounded Schippers, celebrating her 25th birthday, who made a false start in her race but was allowed to continue after signalling to officials that she could not hear.

The Dutchwoman won comfortably in 22.31 seconds before her disqualification was announced and Ivorian Murielle Ahoure, who finished in 22.74, was handed the win.

"It was noisy at the start, so much noise, very hard to concentrate," said Schippers. "Such races happen sometimes so I must accept it."

However, one hour later, the Diamond League organisers tweeted: "Confirmation: Dafne Schippers reinstated as winner in the 200m with a time of 22.31."

No further explanation was given.

De Grasse, hoping to give Usain Bolt a run for his money at the World Championships in London in August, won in 10.01 seconds, one hundredth of a second ahead of Britain's Chijindu Ujah with Ben Youssef Meite of Ivory Coast third in 10.03.

"It felt good, the weather was great, I ran my season best," said De Grasse after winning at the Oslo Diamond League meeting for the second year running.

"I hope it will continue in Stockholm (on Sunday) and I will be able to get my sub-10 before the Canadian trials... for sure I need to improve my start."

Warholm gave the crowd a home win to savour in the 400 hurdles, winning in 48.25 seconds, as Clement slunk home in eighth.

"I had a mis-step at the seventh hurdle, that was the problem," said Clement. "I had nothing afterwards in the last 100 metres. But I hope all will be better in coming weeks, otherwise I felt good."

Wightman upstaged a field including Kenyans Silas Kiplagat and Elijah Manangoi as he won the 1500 metres in a personal best of 3:34.17.

"In utter shock. Can not believe I've just won a Diamond League," the 22-year-old Scot said on Twitter.

Olympic champion Caster Semenya snatched a win in the women's 800 metres as she passed Francine Niyonsaba on the final straight after the Burundian runner led at the bell.