Usain Bolt and Kenenisa Bekele relinquished their world titles on Sunday when the world's fastest man and the most successful distance runner false-started and failed to finish in the 100 and 10,000 metres finals.

Disqualified for leaving the blocks far too early, Jamaican world record holder Usain Bolt left the Daegu arena grimacing and beating a wall with his hand.

He then watched in frustration as his Jamaican training partner Yohan Blake won in 9.92 seconds ahead of American Walter Dix.

However, the triple Olympic sprint champion quickly regained his customary cool.

"Looking for tears?," Bolt asked. "That's not going to happen."

Bekele's sad exit was more protracted. Unbeaten over 10,000 metres on the track, the four-times champion limped off the blue running surface before graciously stopping to talk to banks of television reporters.

"I didn't want to miss this race because I thought I had a chance," said Bekele who hadn't raced since January 2010 after rupturing a calf muscle.

"I am glad I came, I wanted to try," the 29-year-old added. "I was out for two years. The injury is now better, but I am not fit enough. What will I do now? Just keep training."

His title was taken, not by Mo Farah as had been expected, but instead by fellow Ethiopian Ibrahim Jeilan who overhauled the British favourite in the straight.

Blake was ecstatic after taking gold in 9.92 seconds, ahead of American Dix and 35-year-old Kim Collins of St Kitts and Nevis, the 2003 champion.

"It's a wonderful feeling, I have been praying for this moment my whole life," Blake said. "I just tell people anybody can do it, you just stay focussed, pray to God. My training partner Usain Bolt was out and I got the job done."

Bronze medallist Collins lamented Bolt's disqualification.

"As much as I wanted to be on the podium, tonight is a sad night for athletics," he said.

American Brittney Reese successfully defended her world long jump title with her first and only legitimate mark of 6.82 metres. She is the first woman to retain the title since compatriot Jackie Joyner-Kersee in 1991.

Another American Trey Hardee won the decathlon with 8,607 points ahead of compatriot Ashton Eaton and Chinese Li Yanfeng took gold in the women's discus with a throw of 66.52 metres.

Sunday night's drama followed a milestone morning when double amputee Oscar Pistorius made his championship debut running on carbon-fibre prosthetics.

Redefining the concept of athletic achievement, Pistorius clocked 45.39 before 10,000 spectators scattered around the cavernous stadium to witness the first amputee to race at a world championships qualify for the 400 metres semi-finals.

Those who did attend were rewarded with a memorable mental postcard and they roared the 24-year-old round the track, waving placards and screaming him home.

"Being here has been a goal I have had for many years," the South African said.

"I have worked extremely hard to be here and it has been phenomenal to run today," he added.

In the 110 metres hurdles heats, Chinese Liu Xiang looked like the world and Olympic champion he once was and remained on track for a star-quality showdown with American David Oliver and Olympic gold medallist Dayron Robles, who both also eased into the semi-finals.

"It was just the qualification so it was okay," the 2007 world champion and former record holder told reporters. "I'm relaxed and surprised at the results. I think it will take 13 seconds or better to win."