Germany's justice minister has criticized the Vatican for what she called a "wall of silence" over recently emerged abuse allegations.

Sabine Leutheusser-Schnarrenberger said Vatican secrecy rules were complicating investigations of the cases.

Allegations of sexual abuse are being investigated in 18 of Germany's 27 Roman Catholic dioceses.

Former students from a number of Catholic schools have alleged sexual abuse by teachers.

Leutheusser-Schnarrenberger referred to a Vatican rule dating to 2001 that requires abuse cases to be investigated internally.

She expressed dismay at the fact that prosecutors were not called in "as soon as possible."

Allegations of abuse in Germany first emerged in January at the Jesuit-run Canisius College in Berlin, and former pupils at other schools have subsequently come forward.

The cases have led to a discussion over whether to alter Germany's statute of limitations to allow for the prosecution of priests.

The German scandal comes after the Pope led talks last month with Irish bishops over allegations of abuse at schools, orphanages and other institutions in Ireland over several decades.