Jamaica's Usain Bolt kept the showboating to a minimum and swept through to the semi-finals of the men's 200 metres at the world championships on Friday.

Defending champion and world record holder Bolt, who was sensationally disqualified from Sunday's 100 final after a false start, cruised home to win his heat in a time of 20.30.

The lanky Jamaican took off his shoes and stood hands-on-hips watching his performance on the Daegu stadium's giant screen, but apart from a 'thumbs up' to reporters he gave none of his typically flamboyant comments.

Also qualifying for the semi-finals later on Friday were American Walter Dix (20.42) and Frenchman Christophe Lemaitre (20.51).

Dix, who took silver in the 100 behind Blake, oozed confidence and questioned Bolt's readiness for the event.

"I feel that this year it is my stronger event and definitely, I go for gold here," he added. "I am not sure about how Usain is ready. The heat was quite slow. I think that this time it will not be as easy for him as in the past years."

Egyptian Amr Ibrahim Mostafa Seoud ran second in Dix's heat and later collapsed in an area where athletes speak to reporters. Medical staff treated him and he was able to get back to his feet.

"I'm fine, I had a fever five days ago," he told Reuters. "I felt dizzy and I fell down," he added, saying that he still intended to run in the semis.

Bolt, the world's fastest man, had stormed out of the arena after his disqualification in the 100 but later congratulated his Jamaican teammate Yohan Blake on taking his title.

Famous for playing to the crowd with his pre-race antics and trademark victory celebration, Bolt said he would return fully focused on the 200 as well as the 4x100 relay race.

Australian Sally Pearson ran a blistering 12.53 seconds to qualify fastest for the women's 100 metres hurdles at the world championships on Friday.

The Olympic silver medallist, who was hampered by back issues at the last world championships in Berlin, said she had had every intention of running a quick heat to avoid any mishaps.

"Not a bad start, I'm really happy with that," she added.

"I didn't want to take any risks. I really wanted to run that fast so I led it. It's not surprising because I'm in shape."

Pearson has been in dazzling form in the Diamond League this season with three hurdles victories and the world's best time of 12.48 seconds.

Also qualifying for Saturday's semi-finals were Americans Danielle Carruthers, Kellie Wells and Dawn Harper.

Double-amputee Oscar Pistorius, who led South Africa to the final of the 4x400 metres at the world athletics championships, has not been selected for Friday night's final.

The 24-year-old, who ran the first leg of Thursday's momentous race, spoke of his pride following that qualifying heat.

On Friday his response was very different. "Haven't Been included in the Final for the SA Mens 4x400m. Pretty Guttered," he wrote on Twitter.

"Thats me for the ... World Champs! Gods blessed me! Semifinals in the 400m and a National Record in the 4x400m semi! Thank u all!x"

The 4x400m final will be the last race on Friday.