More than 1,500 delegates including people who claim to have had NDEs are attending the one-day conference, which aims to take stock of the disputed phenomenon in the most scientific way possible.
Among them is anaesthetist and intensive care doctor Jean-Jacques Charbonnier, who has taken evidence from several people who claim to have had an NDE.
"People who were brain-dead could see what was going on in a waiting room, or around them, in precise detail. We are not talking about an hallucination here because it was quite real," he said.
Sonia Barkallah, organiser of the conference, being held in Martigues near Marseille, added: "These are people who have come close to death, whether through an accident or during an operation, and who have brought back from their unconscious state accounts that are quite out of the ordinary.
"They are floating above their bodies, they can hear what the doctors are saying about them, they feel themselves getting sucked into a dark tunnel with a bright but not blinding light at the end of it.
"At the end of the tunnel they often meet 'light beings' or dead relatives who tell them it is not their time."
Articles in respected scientific journals such as Nature and The Lancet have provided a better understanding of NDEs, although there remains considerable scepticism about the phenomenon.
"They are floating above their bodies, they can hear what the doctors are saying about them, they feel themselves getting sucked into a dark tunnel with a bright but not blinding light at the end of it"
In a statement released ahead of the conference, delegates including the respected American psychiatrist Raymond Moody said it was "very important that scientists should be able to conduct research in different disciplines, in particular in neurosciences, without prejudice of any kind".
A survey released in 1982 in the United States showed eight million Americans claimed to have experienced an NDE.
Nonetheless, Barkallah said, the phenomenon remains "very controversial, especially in France, where it is difficult to conduct serious research".
"I noticed that doctors were very interested in the subject, but that they conducted their research in secret, afraid of being considered quacks," she said.
"The aim of this international day is not to prove that there is life after death, it is to show what this can teach us on a human and scientific level," she added.
Charbonnier said he frequently felt he could read the minds of his unconscious patients.
He told how on one occasion he felt he was being asked to look in a patient's wallet.
When he did so, he found a letter from the patient asking to be "unplugged" if he was ever in such a condition.
Charbonnier said many people found coming close to death to be a positive experience that left them feeling more altruistic and less attached to material things.