Nepal's top court ordered on Wednesday the release of Charles Sobhraj, the French serial killer portrayed in the Netflix series "The Serpent" who was responsible for a string of murders across Asia in the 1970s.

The Supreme Court ruled Sobhraj, 78, who has been in prison in Nepal since 2003 for murdering two North American tourists, should be freed on health grounds.

Sobhraj began travelling the world in the early 1970s and stayed in Bangkok.

He charmed and befriended his victims -- many of them Western backpackers -- before drugging, robbing and murdering them.

He was implicated in his first murder, that of a young American woman whose body was found on a beach in Pattaya, in 1975.

He was eventually linked to more than 20 killings. His victims were strangled, beaten or burned, and he often used the passports of his male victims to travel to his next destination.

Sobhraj's nickname, "The Serpent", came from his ability to assume other identities in order to evade justice. It became the title of a hit series made by the BBC and Netflix that was based on his life.

He was arrested in India in 1976, after a French tourist died from poisoning at a Delhi hotel, and was sentenced to 12 years for murder.

Sobhraj spent 21 years in jail, with a brief break in 1986 when he escaped and was caught again in the Indian coastal state of Goa.

Released in 1997, Sobhraj retired to Paris but resurfaced in 2003 in Nepal, where he was spotted in Kathmandu's tourist district and arrested.

A court there handed him a life sentence the following year for killing a US tourist in 1975.