Canada's Andre De Grasse added gold to a groaning collection of minor medals with victory in the 200 metres, Kenya went one-two in the men's 800m and Peruth Chemutai made history for Uganda on another scintillating night of Olympic athletics on Wednesday.
Showing perfect judgement he ran down leader Noah Lyles to win in a Canadian record of 19.62 seconds to make him the eighth-fastest man of all time over the distance. After a steady first 500m Korir forged clear to win in 1:45.06 and become a worthy successor to double champion David Rudisha. Muhammad, who led coming off the final barrier, was also inside the world record in second in 51.58, with Dutchwoman Femke Bol running a European record of 52.03 for bronze.
Britain's Katarina Johnson-Thompson pulled up in the 200m, clutching her calf and Germany's Niklas Kaul left the arena in a wheelchair after suffering an injury in the 400m, the final event of the decathlon's first day.