Roman Catholic clerics in Germany sexually abused thousands of children over a 70-year period, Der Spiegel magazine reported on Wednesday, citing a study commissioned by the German Bishops' Conference.

Der Spiegel said the study, conducted by three German universities, had revealed that 1,670 clerics and priests had sexually abused 3,677 minors, mostly males, in Germany between 1946 and 2014.

Asked about the report, a spokesman for the Bishops' Conference told Reuters: 'We are checking the matter.'

He added that the organisation would issue a statement later on Wednesday.

The study examined more than 38,000 personnel and reference files from 27 German dioceses and showed that more than half of the victims were aged at most 13 years old at the time of the crime, Spiegel reported.

The German Bishops' Conference commissioned the 'strictly confidential' study and Cardinal Reinhard Marx, its chairman, is expected to present its findings later this month, Spiegel said.

The Roman Catholic Church, which has more than 1.2 billion adherents worldwide, has grappled in recent years with reports of sexual abuse by clergy that have harmed its moral authority.