STOCKHOLM (AFP) - She calls him by his first name, sends him letters every week, and promises to wait for him. It could be any love story but Victoria's heart belongs to a mass murderer: Anders Behring Breivik.

Responsible for Norway's worst peacetime killing since World War II, Breivik, like many other notorious killers, has his share of admirers, a phenomenon that can be accompanied by sexual attraction and in which case even has a term: hybristophilia.

"I really wouldn't want to live a life without him," says "Victoria", who does not want her real name published.

A young Swedish woman in her 20s, she comes off as distant and standoffish, ignoring her fresh cup of coffee in a Stockholm hotel lobby. But her voice cracks when she talks about her "dearest Anders".

From a small town in Sweden, she is doing everything she can to obtain an easing of Breivik's prison conditions: he has spent the past four years in isolation at a high-security penitentiary.

He is currently serving a 21-year sentence, which can be extended if he is still considered a danger to society.

Breivik killed 77 people on July 22, 2011, when he set off a bomb near the government offices in Oslo and then opened fire on a Labour youth summer camp on the island of Utoya.

For Victoria, Breivik's isolation amounts to "torture".

"I care even more about him now that he is in such a vulnerable situation," she says.

Unemployed because of health issues, she writes to him to help boost his morale - so far more than 150 letters - or sends him small gifts, including a dark blue tie he occasionally wore during his trial.

In return, she has received two letters from him - which she showed to AFP - the others having been blocked by prison officials tasked with censoring his mail.

- Marriage proposals -

It's not easy to define her relationship with Breivik, a man she has never met since all of her requests to visit him have been denied.

She describes him as both her "old friend" and a protective "brother figure", but admits that she finds him attractive and "there were romantic interests, at first, at least from my part."

She says their first contact dates back to 2007 when they met through an online game. He cut off ties with her two years later, most likely to concentrate on planning his attacks.

But in early 2012, Victoria reconnected with the man who by then had become the most hated person in Norway.

And she is not alone.

The weekly Morgenbladet reported last year that Breivik receives "at least" 800 letters a year, many of them from female admirers. During his 2012 trial, it emerged that a 16-year-old girl had asked him to marry her.

Hybristophilia is a term used by criminologists - but not scientists - to describe a sexual attraction to violent killers in prison, who often receive racy love letters or sexy undergarments from their fans.

Also known as the "Bonnie and Clyde syndrome", it has existed throughout time and across borders.

Josef Fritzl of Austria, who held his daughter captive and raped her repeatedly for 25 years, and American killer Charles Manson also have their own fan clubs.

- Often abused women -

According to Sheila Isenberg, an American author who interviewed 30 women for her book Women Who Love Men Who Kill, these admirers often have a history of sexual abuse.

"It's a chance for a woman to be in control (the man is behind bars for life and has no control over anything), when previously she had been abused by her father (or) other men," she explained to AFP.

"Also, it is romance with a capital R: exciting, thrilling, (a) never-ending rollercoaster. Nothing humdrum or ordinary about these relationships."

There is, however, no scientific evidence to support the widespread belief that these women feel they are on a mission to help the killer get on the right track in life, said Amanda Vicary, an assistant professor of psychology at Wesleyan University in the United States.

"Some women tend to be drawn to famous men - it's possible that the reason for some women's attraction to men who have done horrible things is not so much what they've done, but the fame they have received from their acts," she said.

Victoria, meanwhile, says she is not a fame seeker.

Her involvement with Breivik has already cost her her relationship with her sister, who, upon learning of her ties to him, told her: "You're dead to me."

And she has distanced herself from her friends.

She admits to "more or less" sharing Breivik's Islamophobic ideology, but says she is opposed to violence.

So how can she love a man who coldly gunned down dozens of terrified teenagers, some of whom begged him to spare their lives?

"I guess I had to separate Anders from Breivik really. I think of Anders as my old friend and Breivik as the person who did all those things."

The years go by, and yet, she refuses to give up on him.

"I miss him more and more every day. I guess my feelings have gotten a bit stronger."