Ten Spanish priests have been charged with child sexual abuse in a case which court documents show was brought after Pope Francis telephoned the victim to offer the church's apology.

The victim, now 24, wrote to the pope to say he had been molested when he was an altar boy.

In November, Spanish news site Religion Digital reported that the pope called the man last August to apologise, and Francis himself later confirmed this.

Francis also said in November that he had ordered an internal church investigation.

Archbishop of Granada Francisco Javier Martinez removed several priests linked to the case from their duties.

The Granada court said the victim claims the abuse began when he was 14 and lasted until he turned 17.

He said the perpetrators used a house they rented in a suburb of the city.

Earlier reports say the victim has maintained links with the Catholic Church, working as a teacher in a school run by the conservative Opus Dei organisation.

He has told civil authorities he believes other children were abused by the same group and that the ring's members also had sexual relations between themselves.

In April, Pope Francis promised a policy of zero tolerance for sexual abuse of children by clerics after church scandals erupted in several countries over the past 20 years.

However, groups representing victims say he has still not done enough.

The Vatican said last year it had defrocked about 850 priests between 2004 and 2013 after church courts found they had sexually abused minors.