BERLIN (AFP) - Germany's five-times discus world champion and former Olympic gold medallist Lars Riedel announced Wednesday he has retired with immediate effect on health grounds.

"My body is no longer at the necessary level," said the 41-year-old during a press conference in Berlin to publicise his autobiography.

The Olympic champion from the 1996 Olympic Games in Atlanta, and silver medallist at Sydney 2000, has pulled out of next month's Olympic Games in Beijing because of a back injury.

A ten-times German champion, Riedel, an ex-East German athlete, threw his personal best of 71.5 metres in May 1997 - the eighth best throw of all time.

Having not competed since August 2006, Riedel had been set to make his swansong in Beijing, but also pulled out of an athletics meeting in Nuremberg this weekend.

In March 2007, he received a warning from the German Athletics federation for missing a random drugs test carried out by the IAAF.