The renowned Swiss orchestra conductor, Michel Tabachnik, will again have to appear in a French court to answer charges of involvement in the deaths of 16 followers of the Solar Temple Order.
The prosecutor's office in the French city of Grenoble confirmed on Wednesday that it appealed against Tabachnik's acquittal by a penal court last month. Several victims' families have also filed an appeal in a civil court.
Tabachnik said he was being made the victim of legal harassment.
The new trial is scheduled to take place in the first half of next year, but no date has been set yet.
In June the court in Grenoble ruled that Tabachnik was not guilty of criminal association in connection with the deaths of 74 people in France, Canada and Switzerland between 1994 and 1997.
The prosecution had called for five-year prison term for Tabachnik for his alleged role in ritual killings of 16 people, including two children, near Grenoble in December 1995. He was accused of indoctrinating the victims.
The defendant, however, denied the charges.
The Swiss authorities never brought anyone to trial for the deaths of 48 people who perished in two apparent mass-suicides in cantons Valais and Fribourg in 1994. Officials said those believed to responsible for those killings, Jo di Mambro and Luc Jouret, were dead.
swissinfo with agencies