French authorities rejected on Friday an appeal by a former Argentine police officer against his extradition on suspicion he participated in the torture and disappearance of a student during Argentina's military dictatorship in the 1970s.

France's Constitutional Council, which rules on the admissibility of laws and legal rulings, denied Mario Sandoval's request to block the extradition, citing an expiration of the statute of limitations.

Sandoval, 65, is wanted over the alleged kidnapping in October 1976 of Hernan Abriata, an architecture student whose body has not been found since, as well as a slew of other disappearances.

He fled Argentina and obtained French nationality in 1997, prompting his home country to seek an international arrest warrant in 2012 on charges of torture, kidnappings and murder.

Sandoval has denied the accusations, saying they are fabricated.

The French government approved his extradition last August after years of legal wrangling, prompting Sandoval to file his appeal.

The Constitutional Council determined no statute of limitations could be applied to an "ongoing" case, since Abriata's body has never been found.

Abriata was detained at the notorious ESMA navy training school in Buenas Aires, where an estimated 5,000 people were held and tortured after the military coup of 1976 -- many of them thrown from planes into the sea or the Plata river.

The junta pursued what became known as the "Dirty War" until it ceded power in 1983, a period during which human rights groups say some 30,000 people disappeared and were presumably killed.

Argentina suspects that Sandoval took part in over 500 cases of kidnappings, torture and murder because around a dozen people have given testimony against the former police officer.