Nicolas Sarkozy has became the first former head of a European Union state to be jailed, proclaiming his innocence as he entered a Paris prison.
The 70-year-old - president of France from May 2007 to May 2012 - was found guilty last month of seeking to acquire funding from Libya for the campaign that saw him elected.
The right-wing leader - who has appealed the verdict - left his home this morning, and, after a short drive flanked by police on motorbikes, entered La Santé prison.
"Welcome Sarkozy!", "Sarkozy's here", reporters heard inmates shouting from their cells.
One of his lawyers, Christophe Ingrain, said that a request had been immediately filed for his release pending an appeal, but he would still spend at least "three weeks to a month" behind bars.
In a defiant message posted on social media as he was being transferred, Sarkozy denied any wrongdoing.
"It is not a former president of the republic being jailed this morning, but an innocent man," he said on social media.
"The truth will prevail."
"I'm not afraid of prison. I'll keep my head held high, including at the prison gates," Sarkozy told La Tribune Dimanche newspaper ahead of his incarceration.
He was handed a five-year jail term last month for criminal conspiracy over a plan for late Libyan dictator Muammar Gaddafi to fund his electoral campaign.
After the verdict, the former president said that he would "sleep in prison, but with my head held high".
Dozens of supporters and family members had stood outside Sarkozy's home prior to his prison transfer, some holding up framed portraits of him.
"Nicolas, Nicolas! Free Nicolas," they shouted as he left his home, holding hands with his wife, singer Carla Bruni.
Watch: Sarkozy waves to supporters before leaving for prison
Sarkozy is the first French leader to be incarcerated since Philippe Petain, the Nazi collaborationist head of state who was jailed after World War II.
He told Le Figaro newspaper that he would take with him a biography of Jesus and a copy of 'The Count of Monte Cristo', a novel in which an innocent man is sentenced to jail but escapes to take revenge.
Sébastien Cauwel, who heads the country's prison system, said that Sarkozy would be held in isolation.
"He will be able to access the exercise yard, on his own, twice a day, he will have access to an activities room while on his own and he will be alone when inside his prison cell," Mr Cauwel told RTL Radio.
He is being held in a 9 x 12 square metre unit in the solitary confinement wing to avoid contact with other prisoners.
These cells are sparsely furnished, usually containing a bed and desk bolted to the floor, a plastic chair, shelves, a shower and toilet, small hot plate and fridge.
Sarkozy has access to a television - for a monthly fee of €14 - and is able to call pre-approved numbers using a pay phone on the wall.
He will also be allowed visits three times a week. Ms Bruni and one of his lawyers visited him today.
"The first day in prison is terrible, but he got through it," said lawyer Jean-Michel Darrois.
Sarkozy has faced a flurry of legal woes since losing his re-election bid in 2012.
He has also been convicted in two other cases.
In one, he served a sentence for graft - over seeking to secure favours from a judge - under house arrest while wearing an electronic ankle tag, which was removed after several months in May.
In another, France's top court is to rule next month in a case in which he is accused of illegal campaign financing in 2012.
In the so-called "Libyan case", prosecutors said his aides, acting in Sarkozy's name, struck a deal with Colonel Gaddafi in 2005 to illegally fund his victorious presidential election bid two years later.
Investigators believe that in return, the Libyan dictator was promised help to restore his international image after Tripoli was blamed for the 1988 bombing of a passenger jet over Lockerbie in Scotland, and another over Niger in 1989, killing hundreds of passengers.
The court convicted Sarkozy of criminal conspiracy over the plan.
However, it did not conclude that he received or used the funds for his campaign, and acquitted him on charges of embezzling Libyan public funds, passive corruption and illicit financing of an electoral campaign.
Sarkozy had already been stripped of France's highest distinction, his Legion of Honour, following the earlier graft conviction.
Six out of 10 people in France believe the prison sentence to be "fair", according to a survey of more than 1,000 adults conducted by pollster Elabe.
But Sarkozy still enjoys support on the French right and met President Emmanuel Macron last Friday, days before being incarcerated.
Justice minister Gerald Darmanin, who is also close the former president, told France Inter radio that he would visit him in prison.
The isolation unit in La Santé prison, where Sarkozy is being held, has previously housed leftist militant Carlos the Jackal and Panamanian leader Manuel Noriega.
