The Catholic Church in Rome made the extraordinary admission yesterday that it is aware priests from at least 23 countries have been sexually abusing nuns.

Most of the abuse has occurred in Africa, where priests vowed to celibacy, who previously sought out prostitutes, have preyed on nuns to avoid contracting the Aids virus.

Confidential Vatican reports obtained by the National Catholic Reporter, a weekly magazine in the US, have revealed that members of the Catholic clergy have been exploiting their financial and spiritual authority to gain sexual favours from nuns, particularly those from the Third World who are more likely to be culturally conditioned to be subservient to men.

The reports, some of which are recent and some of which have been in circulation for at least seven years, said that such priests had demanded sex in exchange for favours, such as certification to work in a given diocese.

In extreme instances, the priests had made nuns pregnant and then encouraged them to have abortions.

The US article was based on five documents, which senior women from religious orders and priests have presented to the Vatican over the past decade. They describe a particularly bad situation in Africa. In a continent devastated by Aids, nuns, along with early adolescent girls, are perceived by some as safe sexual targets. The reports said that the church authorities had done little to tackle the problem.

The Vatican reports cited countless ca