Anders Behring Breivik, who killed 77 people in Norway last July, has been questioned by the prosecution on his alleged contacts with far-right groups, as they seek to prove that his European network does not exist.
Breivik appeared irritated on Wednesday as he refused to answer questions about the supposed anti-Muslim group he has said he is a part of, during a second day of cross-examination in his trial on terror charges.
Prosecutors have said they believe Breivik's so-called Knights Templar group does not exist "in the way he describes it".
Breivik says it does exist and that police just could not uncover the group.
"It is not in my interest to shed light on details that could lead to arrests," Breivik said.
However, Breivik told the Oslo court that two other cells were prepared to attack the country. When prosecutor Inga Bejer Engh asked if Norwegians should truly fear attacks from two other cells, Breivik answered: "Yes".
Meeting with Serbian
The 33-year-old Breivik says he carried out the attacks on behalf of the organisation, which he described in a 1,500 page document he posted online before the attacks as a nationalist group fighting Muslim "colonisation" of Europe.
Breivik also said he had met a Serbian "war hero" living in exile during a trip to Liberia in 2002, but refused to identify him.
He also refused to give details on what he said was the founding session of the "Knights Templar" in London in 2002.
Al Jazeera's Paul Brennan, reporting from Oslo, said prosecutors were questioning Breivik's credibility.
"They questioned his claims of writing a manifesto for the 'Knights Templar' and Breivik on many occasions refused to answer some of the questions," our correspondent said.
"There were times when Breivik did feel agitated and frustrated by some of the questioning."
Breivik is expected to face further cross-examination on Wednesday.
Breivik's testimony and cross-examination are not being broadcast live, as earlier court proceedings had been, amid concerns that the defendant could use the trial as a platform for far-right views.
In his self-styled manifesto, Breivik described a trial as offering "a stage to the world".
Breivik shot dead 69 people at the youth summer camp on the island of Utoeya after earlier killing eight people in a car bombing in Oslo.
The trial is expected to focus on whether or not Breivik is criminally sane and therefore accountable for his actions.
A first court-ordered psychiatric exam found him insane, while a second opinion came to the opposite conclusion.
If the court decides he is criminally insane, he will be committed to psychiatric care; if he is judged to be mentally stable, he could be sentenced to 21 years in prison, which could subsequently be extended if he was still deemed to pose a threat.