Jefferson Perez strode to a world best in the men's 20 km walk on the opening day of the World championships on Saturday only to learn he would not be collecting a six figure bonus.

Any athlete breaking a world record at the ninth World championships has been promised $100,000 in addition to the winner's prize of $60,000. But because of variations in surfaces, world records are not recognised in road walks.

In 1996 Perez became the first Ecuadorean to win a medal in any Olympic event when he won the 20 km title in Atlanta. He then walked 459 km from Quito to his home town of Cuenca as a religious promise.

"In Ecuador people were starving for this victory," said Perez, whose time of one hour 17 minutes 21 seconds was a second faster than the old mark.

"With the economy so poor, sports is the most important thing for us."

The other titles to be decided on Saturday are the men's shot put and the women's 10,000 metres.

Bahamian Chandra Sturrup, fastest woman in the world this year, clocked 11.08 seconds in the first round of the women's 100 metres. American champion Kelli White won the third heat in 11.26 seconds.

Lima Azimi, one of two Afghanistan athletes entered in the championships, was instructed in the use of starting blocks before heat three. Running in tracksuit trousers, she responded by setting a personal best of 18.37.

Inevitably there were casualties in the opening session.

Shot putter Carl Myerscough, one of Britain's dwindling pool of medal prospects, failed to qualify for Saturday evening's final and Slovenia's European champion Jolanda Ceplak pulled out of the 800 metres.

Ceplak, who might still run the 1,500, aggravated a right Achilles tendon in training.