Charles Sobhraj: Serial killer known as The Serpent to be extradited to France

Sobhraj is suspected of killing more than 20 western backpackers on the 'hippie trail' through Asia

French serial killer, fraudster and thief Charles Sobhraj leaves a Paris court in 1997 with his lawyer Jacques Verges. AFP

The serial killer known as The Serpent has been released from prison in Nepal.

Charles Sobhraj, 78, who spent nearly two decades behind bars, is expected to be extradited to his native France later on Friday.

He is suspected of killing more than 20 western backpackers on the "hippie trail" through Asia, usually by drugging their food or drink in the course of robbing them.

Nepal's Supreme Court on Wednesday ordered his release from prison, citing his age.

He is expected to fly to France on Friday, his lawyer Gopal Shivakoti Chintan told Reuters.

Wearing a woollen cap and a blue fleece jacket, Sobhraj was escorted to Nepal's immigration department by seven police officers.

Earlier on Friday, he was driven from the Central Jail in Kathmandu in a cavalcade of police cars, according to jail official Ishwari Prasad Pandey.

Sobhraj had been held in a high-security prison in Kathmandu since 2003, when he was arrested on charges of murdering American backpacker Connie Jo Bronzich in 1975.

Dubbed the "bikini killer" in Thailand, and "the serpent", for his evasion of police and use of disguises, his exploits have been the subject of several dramatisations, including a Netflix and BBC joint production released last year.

He married Nihita Biswas, a Nepali citizen 44 years his junior, in 2008.

"I'm happy and have great respect for our judiciary and Supreme court," Sobhraj's mother-in-law Sakuntala Thapa told Reuters partner ANI after news of his release was announced.

Sobhraj denied killing the American woman and his lawyers said the charge against him was based on assumption.

Nihita Biswas, who claims to be the wife of Charles Sobhraj. Reuters

Several years later Sobhraj was also found guilty of killing Bronzich's Canadian friend, Laurent Carriere.

But he was suspected of many more murders, including in Thailand, where police say he allegedly drugged and killed six women in the 1970s, some of whom were found dead on a beach near the resort of Pattaya.

He was jailed in India for poisoning a group of French tourists in the capital, New Delhi, in 1976, before he could stand trial on the charges against him in Thailand.

Sobhraj escaped from Tihar jail in India in 1986 after drugging prison guards with cakes laced with sleeping pills.

Police arrested Sobhraj days later in the Indian beach holiday state of Goa.

"I walked up to their table and said 'you are Charles'", Madhukar Zende, the police officer who caught him in Goa, told The Indian Express newspaper in an interview published on Friday.

A statue of Sobhraj stands at the restaurant in Goa to this day. He was jailed in India until 1997 when he returned to France.

Born to a Vietnamese mother and Indian father, he was described by his associates as a con artist, a seducer, a robber and a murderer.

His true number of victims, spanning decades and several countries, is unknown.