A specially created police unit will conduct the investigation, the biggest in Norway's history, into all aspects of the July 22 bombing in Oslo and the shooting spree on nearby Utoeya island. Breivik, 32, has confessed to the attacks.

Some of the 100 investigators now on the case are checking whether Breivik had financial help, a senior officer told Reuters, and are seeking clues in Bermuda, Antigua-and-Barbuda and other off-shore tax havens whose banks are not fully transparent.

"In the interviews he (Breivik) has said he worked for a long time and saved a lot of money to finance his activities later," police prosecutor Paal-Fredrik Hjort Kraby said in an interview.

"It was several million Norwegian crowns -- I won't comment on the exact number -- and he said it was from his own work, not from anyone else."

In a manifesto Breivik boasted that he earned 4 million crowns ($743,200) for his plot by 2005 and channeled some through the Caribbean and eastern Europe before losing about half in "stock speculation" by 2008.

Reuters