England, Australia and the USA teams are being given additional security because of a "low risk" of terrorist attacks at the World Cup.
England are among those training amid tight security
The three countries were all involved in the war on Iraq and, as a result, their position is being monitored more closely, said Australian Rugby chiefs.
Australian Rugby Union chief executive John O'Neill said: "Some teams are a higher risk than others.
"The USA, England and Australia are teams that have been assessed as
deserving a higher risk category and there are additional
precautions surrounding them."
The tournamnet begins with the game between Australia and Argentina, just two days before the one-year anniversary of the Bali nightclub bombing in Indonesia.
"We have got the best possible advice from state and federal government and the best scrutiny agencies Australia can muster," said O'Neill.
"No stone has been left unturned. The tournament is rated low risk but we're treating it as a medium risk on the basis that it is easier to scale down measures rather than scale up."