PARIS (AFP) - Jerome Kerviel, the French rogue trader who brought one of Europe's biggest banks to the verge of ruin with nearly 5 billion euros (S$8.11 billion) in losses, left prison on Monday after winning conditional release.

Under the terms of his release, Kerviel, 37, will be obliged to wear an electronic tagging bracelet at all times and stay at home every workday evening.

He left Fleury Merogis prison, south of Paris, after less than five months following his high-profile conviction and imprisonment for breach of trust, forgery and entering false data.

"I am super happy to leave today ... I want to rebuild my life. I want to have a normal life with my loved ones, start a family and finally be able to enjoy life," Kerviel told reporters as he left the prison.

He said he "couldn't wait to phone" his mother, who he said had broken down when the prosecutor launched an appeal against his conditional release.

He also paid tribute to the prison staff during his isolation in prison and said his time spent behind bars had been in some ways "enriching" and had changed his view of the penal system.

"I am super happy to leave today. It will be easier - for me of course and for my loved ones - and easier to work on the case, to continue this fight," the former trader said.

Wearing an electronic bracelet is "always better than being shut up" in a 9 sq m cell, said the former trader, who was unshaven and wearing a white T-shirt under a black pullover.

"Today is a day of immense joy for us. Immense joy," said Kerviel's lawyer David Koubbi, who told reporters the "fight" against Kerviel's former employer Societe Generale would continue.

"It's true that an electronic bracelet is a constraint but it's not the same constraint as being here," he said.

The former trader brought banking giant Societe Generale to its knees in 2008 with wildly risky trades of up to 50 billion euros on derivatives - betting on the market direction.

Kerviel became something of a cause celebre in France and overseas with many saying he had been set up as a scapegoat for the failings of the wider financial system.

The trader himself said he was ashamed of his former profession and embarked on a two-month trek through Italy to protest the "tyranny of the markets", even winning an audience with Pope Francis.

Kerviel will have to wear the bracelet until June 26 next year and his movements are restricted. He must be at home between 8:30pm and 7am between Monday to Friday.

His lawyer has said previously Kerviel has secured a job at an IT consultancy firm and hopes to resume "a completely normal life".

Kerviel never denied making huge gambles. "My daily existence was about making money for the bank. That was my only objective, at any price, regardless of all moral or ethical considerations," he said before.

Despite dealing in such vast sums of money, he was on a relatively modest 50,000 euro basic salary when the scandal erupted in January 2008.

He lived in an unremarkable, small suburban flat and took the train to Brittany in the holidays to visit his widowed mother.

"I am an ordinary person. I'm not crazy," he said during investigations into the scandal.

"I didn't earn millions (in salary) and I didn't drive a Porsche."said Kerviel, who was paid 50,000 euros a year plus tens of thousands more in bonuses when the scandal erupted in January 2008.

"Have you seen my apartment? 45 sq m, no masters' paintings. Ikea furniture," he added.

Some commentators have interpreted his big risk-taking as motivated by the desire to prove himself, a young man from a modest background, among the ranks of high-flying traders from elite schools.

Societe Generale says he worked out how to circumvent complex risk-control mechanisms and its lawyer Jean Veil accused him of "duplicity" in reassuring his employers that all was well.

Kerviel was born in the small town of Pont l'Abbe, Brittany, to a father who taught metalwork and a mother who was a hairdresser.

He once ran for municipal office as a candidate from former president Nicolas Sarkozy's conservative UMP party but was not elected. He told the newspaper Liberation that as a child he wanted to be a vet.

Instead, Kerviel trained in economics and finance at universities in nearby Quimper and in Nantes and Lyon, where his teachers said he graduated with solid but not exceptional grades.

He joined Societe Generale in 2000 and, five years later, was promoted to the "front office" to trade futures on European share indices - effectively betting on the direction of the stock market.

Colleagues at the time described him as a quiet loner. Journalists have likened the fresh-faced ex-trader to the film star Tom Cruise.

He liked the music of R and B singer Alicia Keys and was a big film fan, admitting that he cried at the end of the 3D fantasy "Avatar".

Kerviel spent 38 days in custody after his arrest in 2008 and later took up a job at a small IT company in a suburb of Paris.

He said ahead of his initial trial that he hoped it would teach people the lessons of the global financial crisis.

"Respect for work, solidarity, honesty - I grew up with these notions. But when I became a trader, I lost part of these morals."

In a bid to raise awareness, he embarked on a trek from Rome to Paris to highlight the "tyranny of the markets", even securing an audience with Pope Francis.

His new arrangements will suit a modest man.