Oscar Pistorius of South Africa (L) runs past Femi Ogunode of Qatar during the men's 400 metres heats at the IAAF World Championships in Daegu, Aug 28, 2011. [Photo/Agencies]

DAEGU, South Korea - "Blade runner" Oscar Pistorius passed his first test with flying colours on his world championships debut by finishing third in his heat to reach the semi-finals of the 400 metres on Sunday.

The South African, who has had to overcome huge legal and performance obstacles just to be allowed to race in Daegu on his prosthetic legs, delighted the crowd with a strong run of 45.39 seconds from an outside lane.

The crowd rose to the double amputee as he powered down the final straight before a band of his compatriots chanted "Oscar! Oscar!" to confirm the 24-year-old as one of the sentimental favourites of the championships.

Describing his landmark race as a "great relief" especially after the disruption of a false start by another of the runners, Pistorius said he had fulfilled a long-held ambition.

"It was a great opportunity for me to have a chance to run, this is a goal I've had for many, many years," he told reporters.

"I really don't feel like a pioneer but I'm very honoured to be in the position I am in ... I hope to write a few more chapters, I'm still young."

Noting that other heats had been faster, Pistorius, whose time was the second fastest of his career, said he thought Monday's semi-final might be the end of the road for him in Daegu.

"Today my goal was to be consistent, it was difficult running from lane eight, I know tomorrow's going to be much more challenging," he said.

Oscar Pistorius of South Africa comes out of the starting blocks during his men's 400 metres heat at the IAAF World Championships in Daegu, Aug 28, 2011. [Photo/Agencies]

Earlier, defending champion LaShawn Merritt of the US had stamped his authority on the event with the fastest time of the year of 44.35 to win his heat in impressive style.

The American, also the Olympic champion, had raced just once before Sunday since returning from a 21-month doping suspension in July. "I've never worked harder, it was a little faster than I thought it would be but I was comfortable," he said.

Merritt confirmed that Pistorius's story had inspired not only the crowd. "He ran the time to get here, I had a little time to talk to him and he's a great person with a great personality," he said. "He's dedicated and motivated and has a great heart. I wish all the best to him."

Young Grenadans Kirani James (45.12) and Rondell Bartholomew (44.82), the fastest men this year before Merritt's run on Sunday, also eased into Monday's semi-finals.

American champion Tony McQuay, who owned the fourth best time of the year, made a surprise exit, however, after pulling up with a hamstring strain.