An author cited in the Norway massacre suspect's rambling, 1,500-page manifesto expressed regret Monday that her writing might have served to inspire his rampage.
Gisele Littman, who writes under the name Bat Ye'or, said that since her books are in the public domain she had no control over who quoted her.
"Of course I regret if this man took inspiration from what I wrote or from what other writers wrote," she told The Associated Press by telephone from her home in Switzerland. "As an insane person he should have been treated before, and I am greatly saddened for all the young innocents who tragically lost their lives, and for their families."
Breivik cites Littman's work approvingly many times in the document he posted shortly before Friday's attacks.
Her 2005 book "Eurabia: the Euro-Arab Axis" explores the relationship between European and Muslim countries. The term 'Eurabia' has been used by some to describe the growing influence of Islam in Europe, though Littman contended that her arguments are more complex.
She said some Europeans harbor a suppressed fear of Islamic colonization that might erupt into violence.
"I think there is a lot of frustration, for instance in France and England, and I think discussions in our society should be encouraged," said Littman.
Referring to Breivik's attack, she added: "I'm afraid that this is something other people will imitate."
"I think the police must be very vigilant. This problem of Norway is a problem of Europe," said Littman, whose next book is titled "Europe, Globalization, and the Coming Universal Caliphate."
Littman is a Cairo-born Jew whose website says she fled the country in the 1950s after her nationality was revoked. She settled in England, where she married, before moving to Switzerland.
(This version CORRECTS word to page in first paragraph)