PARIS (REUTERS) - French fashion designer Sonia Rykiel died on Thursday (Aug 25) at the age of 86, mourned by President Francois Hollande as an inventor of "an attitude, a way of life".

Rykiel was a rare woman at the top of a world dominated in the 1970s, 1980s and early 1990s by men such as Yves Saint Laurent and Karl Lagerfeld, inspiring female self-empowerment through her tongue-in-cheek style, notably brightly striped sweater dresses.

"It is a sad day, but Sonia Rykiel leaves behind her an extraordinary legacy," Jean-Marc Loubier, chairman and chief executive of First Heritage Brands, parent company of the Sonia Rykiel label, told Reuters.

"She was a pioneer who helped women and society evolve."

Instantly recognisable by her bushy red hair, Rykiel founded her fashion house in the literary Paris quarter Saint-Germain des Pres in 1968, when France was rocked by violent student riots, aiming to counter stiff, bourgeois dress codes, with inside-out stitches and extra-short skirts.

Early adopters of her tightly fitting sweater dresses included actresses Brigitte Bardot, Catherine Deneuve and Audrey Hepburn.

"I wanted to make a sweater for a specific woman - myself," she wrote in her 2012 memoir "N'oubliez pas que je joue" ("Don't forget that I am acting").

"(I) couldn't find the clothes I had in mind for a woman of 30 who has come home from work to go to the theatre and then wants to go out for dinner afterwards.

"I had the sweater made in a factory in Italy and it was tiny; it was just how I wanted it. They called it the 'poor boy sweater'. Someone from French Elle saw it in the shop window, and it made the front cover."

President Francois Hollande's office said: "She had invented not only a style but an attitude, a way of life and gave women freedom of movement."

Ralph Toledano, chairman of the French Federation of couture, ready-to-wear designers and fashion designers said: "Sonia Rykiel was a great lady of exceptional talent, she embodied the rebel and independent spirit of Paris and Saint Germain des Pres."

"Her style expressed the quintessence of a free woman and her heritage is all the more pertinent in light of the current news and events," he said, a reference to the decision by many French seaside towns to ban "burkinis".

In the 1970s, Women's Wear Daily called Rykiel "the queen of knitwear" even though she never learned how to knit and had not studied fashion.

In 1995, Rykiel passed on the creative and management leadership to her daughter Nathalie, around the time she was diagnosed with Parkinson's disease.

In 2012, the family sold control of the label to Hong Kong investors but Nathalie Rykiel still works as a consultant for the fashion brand.