Pictures and videos circulating online and also shared by local state authorities showed a shirtless Joshua 鈥 a British national of Nigerian heritage 鈥 grimacing in pain as he was helped step out of the car.
Others showed a mangled wreckage of a black sports utility vehicle.
His promoter Matchroom said the boxer鈥檚 鈥渃lose friends and team members鈥 Sina Ghami and Latif Ayodele were killed and Joshua himself was taken to hospital 鈥渇or checks and treatment鈥.
Nigerian police said the two victims died 鈥渁t the scene鈥.
Joshua鈥檚 family hails from the southwest Nigerian city and he is known to visit there when he is in the country.
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