A notorious French serial killer suspected of killing over a dozen people across several countries has been released from prison in Nepal after 19 years.

Charles Sobhraj walked out of prison in Nepal on Friday and was taken to the airport to head back to his native France after being released 19 years into his life sentence, which in Nepal is 20 years, for killing American and Canadian backpackers. 

The Supreme Court had ordered that Sobhraj be freed because of poor health, good behavior and having served more than 75% of his sentence, making him eligible for release. It said Sobhraj has heart disease.

The 78-year-old French national is believed to have killed at least 20 people in Afghanistan, India, Thailand, Turkey, Nepal, Iran and Hong Kong during the 1970s. His 2004 conviction in Nepal was the first time he was found guilty in court.

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Charles Sobhraj

Nepalese police escort Charles Sobhraj, in brown cap, to the immigration office, in Kathmandu, Nepal, Friday, Dec. 23, 2022.  (AP Photo/Niranjan Shrestha)

Sobhraj, who preyed mostly on young backpackers on the "hippie trail" through Asia, usually by drugging their food or drink in the course of robbing them, was featured in the 2021 Netflix drama series "The Serpent".

Sobhraj earned the nickname "Serpent" from the disguises he used to evade police over the years and was known as the "bikini killer" in Thailand due to the attire many of his suspected victims were wearing.

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Charles Sobhraj

French serial killer Charles Sobhraj is escorted by Nepalese police at a district court for a hearing on a case related to the murder of Canadian backpacker Laurent Ormond Carriere, in Bhaktapur on June 12, 2014.  (PRAKASH MATHEMA/AFP via Getty Images)

After his release, Sobhraj told news agency AFP that he planned to sue the people who put him behind bars saying, "I feel great... I have a lot to do. I have to sue a lot of people. Including the state of Nepal."

Sobhraj maintained his innocence to a reporter on the plane before departing for France, AFP reported.

"I am innocent in those cases, ok? So I don't have to feel bad for that, or good. I am innocent. It was built on fake documents," Sobhraj said.

While in prison, Sobhraj married Nihita Biswas, a Nepali woman 44 years his junior, in 2008.

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. (AP Photo/Niranjan Shrestha)v

Charles Sobhraj's lawyer Gopal Siwakoti, right, talks to media outside immigration office, in Kathmandu, Nepal, Friday, Dec. 23, 2022.  (AP Images)

"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.

THE Associated Press and Reuters contributed to this report.