Breivik is hesitant about revealing too much on the matter as he says he doesn’t want to expose his comrades to arrest.
However, prosecutors think the reason for his reticence is that the secret network is a figment of Breivik’s imagination.
The accused killer has told of how he was in Liberia in 2001 he met a Serbian nationalist.
He has said he was a member of a group called the Knights Templar. Prosecutors do not believe it exists.
Prosecutors displayed an excerpt from Breivik’s 1,500-page manifesto in which he said he had contacts with “Serbian cultural conservatives”.
Breivik wrote that they did a “complete screening and background check” to ensure that he was of “the desired calibre”.
He claimed the group was considering “several hundred” individuals throughout Europe for a training course.
His testimony and that of his witnesses is not being broadcast. His testimony is expected to last for five days.