Norway's TV2 reported that Anders Breivik, 32, released a video and document to the web a few hours before a bomb exploded in downtown Oslo, killing 7 people and damaging a government building.
TV2 said police confirmed that Breivik confessed to publishing the material, appearing on Friday.
The video advocates for fighting against cultural Marxism and Islamism.
The document describes the bombing as a martyrdom operation.
The video, which contains the name Andrew Berwick is entitled 2083 - A European Declaration of Independence.
The accompanying document, which is more than 1,500 pages long extolls his political views and contains what appears to be a self-reported detailed account of his activities in the months before the bombing until July 22, the day the operation was to take place.