Evidence suggests rightwing extremist Anders Behring Breivik carried out his deadly attacks alone, Norwegian police said Saturday, adding they would be more confrontational in a new interrogation next week. "We are trying to identify any people he might have cooperated with. So far, everything suggests he was alone. We will question him again early next week," police prosecutor Christian Hatlo told AFP, adding it was however too early to rule out that the self-confessed perpetrator of the July 22 atttacks had help. "Everything points out that he was alone on the actual acts. The thing we are looking into is if he might have bought something illegally" and if the people who sold him equipment knew of his intentions, he said. Next week's interrogation of Behring Breivik, a 32-year-old Norwegian, will be more confrontational, Hatlo said, adding that police knew he was holding back information. "Up to now he has been talking more or less freely but we have started to confront him more ... he is withholding information that could lead police to some more people," he said. Investogators will also seek to get a better look into his finances. Behring Breivik has said he gathered large sums of cash and the police "have to control if it's true he was able to gather that much money on his own," Hatlo said. Hatlo added that a Norwegian blogger Behring Breivik had identified as "his favourite contemporary author" was considered a witness in the probe, and that the far-right blogger's computer was being searched. On July 22, Behring Breivik set off a bomb near the offices of Norway's Labour-led government in central Oslo, killing eight people. Hours later, he went on a shooting rampage on an island near the capital where the Labour party youth wing was holding its summer retreat, killing 69 more, many of them teenagers. He is currently in custody in isolation at a high security prison near Oslo. Police have interrogated him three times since his arrest the day of the attacks, for a total of 30 hours, according to Norwegian media. Behring Breivik sees himself as a "crusader" on a mission to halt Europe's "Islamicisation" and multiculturalism. He has described his acts as "cruel" but "necessary."