Moroccan Jamel Chatbi pleaded his innocence on Tuesday after a positive test for the banned stimulant clenbuterol made him the first doping casualty of the world athletics championships.

An 'A' sample from Chatbi, who had been due to compete in the 3000 metres steeplechase final later on Tuesday, taken on Saturday tested positive for clenbuterol, according to a statement from the Moroccan federation.

But the 25-year-old who was recently crowned Mediterranean Games champion in Pescara, Italy, refuted all allegations that he had taken a performance-enhancing product.

"I'm innocent. I've never taken any doping products and I'm ready to fight my case in front of the IAAF and the CAS (Court of Arbitration for Sport) if I have to," said Chatbi.

Clenbuterol, which is on the banned list, is a stimulant but in medicine is used to help asthma sufferers and those with respiratory problems to breathe.

This season Chatbi had shown a remarkable improvement, slashing more than 13 seconds off his personal best taking it to 8min 08.86secs from 8:22.16.

He is the first athlete to fail a dope test at the championships, which began on Saturday and end on Sunday.

Athletics' world ruling body the IAAF confirmed the news to AFP through its spokesman Nick Davies, adding that Chatbi would not line up for the final.

Chatbi later said the positive test may have been down to antibiotics prescribed to him by an Italian doctor.

"I've suffered from a nasal allergy since the end of last year and I consulted an Italian doctor who advised me to take antibiotics," added Chatbi.

"But after having a blood sample analysed I had to undergo an operation last March. Maybe the antibiotics contained this product.

"If it's the case then I didn't know. But I insist, I've never taken doping products."

On Monday the IAAF said it had carried out 590 doping controls since the first athletes started arriving in the German capital on August 11.

The world body said it took 450 blood samples from athletes, which will be tested for growth hormones, EPO (erythropoietin) CERA and blood transfusions, and 140 urine samples.