PARIS — Moroccan-born Leila Slimani won France’s top literary prize, the Goncourt, on Thursday with a novel guaranteed to "scare the wits out of parents".

The chilling tale of a "perfect" nanny who murders the two children she is looking after, Chanson douce (roughly translated as "Sweet Song") is based on the real-life story of a Dominican child-minder shortly to stand trial for the double murder of her charges in New York in 2012.

The book – which begins with the words "the baby is dead" – is already a bestseller in France.

A mother herself, 35-year-old Slimani, who caused a stir with her first book about a female nymphomaniac, said "the idea of paying someone to love your children for you" fascinated her.

"It leads to a very ambiguous relationship... We are always afraid they will steal our place in our children’s hearts," said the writer, who is pregnant with her second child.

"I had nannies when I was a child and I was always very aware of their place somewhere between a mother a stranger," she said.

"I was touched by the difficult position they found themselves in," said the former journalist.

Slimani is only the 12th woman to have won the Goncourt in its more than a century-long history, joining a list that includes Marguerite Duras and Simone de Beauvoir.

Mobbed by reporters outside the Paris restaurant where the prize was announced, she said: "It is hard to talk about literature in this craziness".

’X-rated’

Despite being favourite, she said that she "slept well last night, maybe because it was going to turn out well".

She dedicated the prize to her parents, "My father who died 10 years ago and my mother who arrived from Morocco this morning and had an intuition that I would win at 4am," she added.

Critics said her book – which transposes the essentials of the notorious killings of the Krim children, Lucia, six, and her two-year-old brother Leo to a wealthy Parisian family – crackled with class tensions.

The writer made headlines with her debut novel last year about sex addiction, Dans le jardin de l’ogre (In the Garden of the Ogre), which was partly inspired by the private life of the disgraced French politician Dominique Strauss-Kahn.

Her mother, a doctor, described the book as a kind of "X-rated Madame Bovary".

Although Slimani gets only 10 euros (US$11) in prize money, the Goncourt almost guarantees a boost in sales of 450,000 copies or more, placing it instantly among the year’s top bestsellers.

For a prize that is meant to celebrate the very best of French fiction, this year’s race was dominated by books which drew their inspiration directly from real events.

The highly-fancied debut novel by rapper Gael Faye Petit pays (Little Country) is a beautifully written coming of age story based on the 34-year-old’s own childhood in Burundi, while Catherine Cusset’s L’autre qu’on adorait (The Other One We Loved) recounts a former lover’s slide into depression and suicide.

Two women and two men made up the gender-balanced shortlist, with Regis Jauffret also flirting with the autobiographical in his dark epistolary novel Cannibales.

The separate Renaudot prize, often seen as something of a consolation prize, went to Babylone by Yasmina Reza, best known for her hit play Art.

Like the Goncourt winner, it too is a kind of crime novel in which a dinner party dispute over free-range chicken has fatal consequences.  — AFP