They have been punished by team chiefs because they refused to train with the bulk of the team in Nuremberg and stayed with coach Stephen Francis at their Italian training camp in Lignano Sabbiadoro.

The move adds to a turbulent build- up for the Jamaicans after five athletes failed a dope test but were subsequently cleared by their national anti-doping commission.

Meanwhile, the championships, which get underway on Saturday, are to be the target of the most comprehensive drug-testing program in history.

More than 1,000 blood and urine samples will be collected, before and during the competition.

International Association of Athletics Federations president Lamine Diack said the championships were a chance to recognize `clean' athletes. "I would like to turn our attention back to the huge majority of honest athletes who will compete based on their own skill and years of hard work and sacrifice," Diack said.

Around 600 blood samples will be taken prior to the championships and another 400 blood and urine samples taken during the competition itself, all to be sent to the World Anti-Doping Agency-accredited laboratories in Cologne and Dresden.

Diack added: "Athletes should be well aware that not only do we have the possibility to store samples, but that already in the past year the IAAF has prosecuted several cases based on re- analyzed samples.

"If they think they can turn up with an undetectable drug and get away with it, then they may be in for a shock." Jenn Stuczynski, women's pole vault runner-up at the Beijing Olympics, will not compete at the championships due to a sore Achilles tendon.

AGENCE FRANCE-PRESSE