* Police say gunman likely alone but don't rule out helpers

* Analysts say question existence of Knights Templar group

* Gunman's manifesto calls for disinformation

OSLO - Norwegian police think gunman Anders Behring Breivik is probably a lone wolf, a view also held by some researchers who cast doubt on his claim that he was working with two other cells.

Breivik, who admitted to carrying out a bomb attack and shooting spree last Friday that killed 76 people, told a court on Monday that two cells of collaborators were in his "Knights Templar" group that aimed to "save" Europe from Muslims.

Earlier, Breivik maintained he acted alone.

Police attorney Christian Hatlo told reporters on Monday he "cannot completely, and I stress completely, rule out that others were involved in what happened."

But police say privately that they think more cells are unlikely although security services are checking with their international partners about potential foreign links.

"We feel that the accused has fairly low credibility when it comes to this claim but none of us dare to be completely dismissive about it either," a source close to the investigation told Reuters.

Police are checking Breivik's phone and credit card records as well as his known movements to determine whether he was working alone.  

Magnus Ranstorp, Research Director at the Centre for Asymmetric Threat Studies at the Swedish National Defence College, said that, as far as he knows, nobody had evidence of the existence of the Knights Templar organisation.

"There's no one who seems to know if the group exist or if it's something he made up," he told Reuters. "They (mass killers) are usually alone. He's extremely narcissistic and he goes on about himself and his role in history."

Ragnhild Bjoernebekk, a researcher at Norway's police school who specialises in crime and violence, said it was not inconceivable that Breivik was part of a network, but added:

"The fact he wants to talk about it is surprising. Perhaps he wants to suggest that he is part of something bigger than himself," she said.

Further undermining his claim, Breivik's manifesto published before his shooting rampage suggested authorities should be disinformed about collaborators.

"Give the impression that your cell is larger by attempting to forward misinformation on the police band or by other means," he said in the 1,500 page document.

In the rambling manifesto, which mixes imagery of medieval crusades and Internet war games, Breivik calls himself a "Justiciar Knight Commander of Cell 8" and said he would try to "initiate contact with cell 8b and 8c".

The document says that each cell commander has up to two operatives.

"Intuitively, it feels like he is alone when you read the document. It's like he's lost in this made up world and can't distinguish between fantasy and reality," said Ranstorp.

(Additional reporting by Johan Ahlander, Kjetil Stormark and Ole Petter Skonnord, editing by Myra MacDonald)