Kenya’s Timothy Cheruiyot, favorite for the world 1500 meters title, comfortably won his opening heat on Thursday, evading the rough-and-tumble which saw Ethiopia’s Teddese Lemi falling.
Lemi was in second place approaching the bell in the second heat as jostling began among the pack of runners.
At one point, Norway’s Filip Ingebrigtsen appeared to nudge Lemi in the back and he tumbled over.
Lemi got up and continued but finished 11th and failed to qualify while Ingebrigtsen went on to finish fourth to ensure his place in the semi-finals.
Ingebrigtsen’s younger brother Jakob, the European champion, also went through by winning the first heat as did Olympic champion Matt Centrowitz.
Djibouti’s Ayanleh Souleiman won the third heat ahead of Algeria’s 2012 Olympic champion Taoufik Makhloufi.
Elijah Manangoi of Kenya was unable to defend his title after suffering an ankle injury in training.