And for the first time it has warned against mistaking diabolic possession of the spirit with mental illness.

The BBC's Rome correspondent, David Willey, reports on the new exorcism guidebook

Pope John Paul II himself has approved the guidelines for deciding when and how to perform exorcisms, last issued in 1614.

Except for some new formulas for priests authorised by bishops to read during exorcisms, the text is largely unchanged. What is new is the caution that determines if exorcism is warranted.

"The exorcist will decide with prudence" after consulting with spiritual experts and "if considered opportune, with experts in medical and psychiatric science," the new rules stress.

So far the new rite is available only in Latin, bound in a red, leather-bound, 84-page book with red bookmark, but it will be translated into modern languages.

During his papacy, the Pope has denounced the devil in a series of homilies as a "cosmic liar and murderer" although opinion polls indicate the devil has largely slipped out of Christian consciousness.

Cardinal Jorge Medina Estevez shows off the new guidelines

"The existence of the devil isn't an opinion, something to take or leave as you wish," said Cardinal Jorge Medina Estevez, a Vatican official, adding that belief in Satan was a tenet of Catholic faith.

The devil "deceives men, making them believe that you find happiness in money, in power, in carnal desire," said the cardinal who presented the revised rules.

Signs of the devil's presence are said to include:

• Speaking unknown languages
• Displaying strength disproportionate to a person's age or body.

The rite of exorcism itself remains essentially the same, including making the sign of the cross, sprinkling holy water and ordering the devil to leave the possessed person.

People convinced they are victims of the "evil eye" and other curses do not need exorcisms, say the rules, but special prayers are suggested.

Vatican officials said they had no figures on how many exorcisms were performed, but major dioceses do have their own exorcists.

Media ban

One new rule is a ban on media coverage of exorcisms. A 1991 exorcism in Florida of a young girl was filmed for US network television.

The Pope himself once performed an exorcism during his papacy, according to the memoirs of Cardinal Jacques Martin, the former prefect of the pontifical household.

Quoting the late cardinal's book, "My Six Popes," the Italian news agency ANSA said Pope John Paul II carried out the rite in 1982, driving out the devil from a woman who was brought to him, writhing on the ground.