The self-confessed perpetrator of last month’s twin attacks in Norway was reportedly interrogated for a third time yesterday as police said they would be harsher and more confrontational in their questioning.

The Norwegian daily VG published a picture on its website of a van it said had transported the confessed killer, rightwing extremist Anders Behring Breivik, to Oslo police headquarters at around 9 a.m. (0700 GMT) for interrogation.

While police prosecutor Paal-Fredrik Hjort Kraby would not confirm the report, he told a news conference that questioning would happen this week and “we can say that what will be central to that interrogation is that it will be more confrontational”.

Police would only confirm the interrogation after it had taken place, he said, adding that while it appeared the 32-year-old killer had acted alone, investigators would push especially hard for information about any possible accomplices.

“That’s the main issue because if we find someone else, the investigation changes completely. But he’s been very specific that he (acted) all alone,” Hjort Kraby said.

He said Mr Behring Breivik, who claims to be on a “crusade” against a “Muslim invasion” of Europe, “could” have acted alone.