An octogenarian German ex-doctor imprisoned in France for killing his 14-year-old step-daughter 38 years ago was freed Friday for medical reasons, a source close to the case told AFP.

This brings to a close a dramatic story that saw the former cardiologist, Dieter Krombach, kidnapped in Germany by his victim's father and brought to France to stand trial.

Krombach was convicted by a French court in 2011 and given a 15-year prison term.

Last October, a parole committee decreed his sentence should be suspended on medical grounds, which resulted in the doctor, now 84, taken away by ambulance from a prison near Paris on Friday morning.

A German investigation in 1987 had found there was not enough evidence to charge Krombach of the murder of Kalinka Bamberski, found dead in her bed during the summer holidays of 1982.

But the doctor's credibility was damaged when in 1997 he was found guilty of drugging and raping a 16-year-old patient, emboldening Bamberski's biological father, Andre, in his campaign to see Krombach arrested.

Frustrated with Germany's refusal to hand Krombach over, Bamberski hired a kidnap team to snatch the doctor from his home in Scheidegg, Bavaria, and bring him to France.

The doctor was left, bound and gagged, near a courthouse in the border town of Mulhouse, and later put on trial.

After Krombach was convicted by a French court in 2011, Kalinka's father was also put on trial and convicted in 2014 over the kidnapping. He was handed a suspended one-year jail sentence.

The two men who carried out the kidnapping - Anton Krasniqi of Kosovo and Georgian Kacha Bablovani - were sentenced to a year in prison each.

The drama of Andre Bamberski's fight for justice has been turned into the 2016 movie, "Au Nom de Ma Fille," with the English title "Kalinka".