STRASBOURG, April 22 — French prosecutors announced Tuesday an international arrest warrant for a leading figure in conspiracy circles who is suspected of helping to organise the kidnapping of an eight-year-old girl that gripped the country last week.

The girl, identified as Mia, was found with her 28-year-old mother Lola Montemaggi on Sunday by police in Switzerland, following an intense five-day search after she was taken from her grandmother's home in Poulieres, eastern France.

Five men as well as Montemaggi have been detained over the abduction, which saw three of the men pose as child welfare officials to convince the grandmother to hand Mia over.

Prosecutors say that the plot was code-named "Operation Lima," and that they had walkie-talkies, camping gear, fake licence plates and a budget of €3,000 (RM14,840) to cover expenses.

They said the mother's associates in the kidnapping plan were anti-system activists who believe that "children in care are unfairly taken from their parents."

After questioning the suspects, investigators say they may have been helped by Remy Daillet, known to French police as a proponent of extremist conspiracy theories and a populist takeover of the state.

Daillet, 54, was a former regional leader of the centrist MoDem party before he was excluded in 2010.

Known to police

French daily Le Parisien reported Tuesday that he has been living in Malaysia for several years.

"Remy Daillet appears to be a leading organiser of the 'movement' to which the suspects belong," state prosecutor Francois Perain in the eastern city of Nancy said in a statement.

He may also have "played a role in organising the kidnapping and provided the contact details for the person who took in the mother and child in Neuchatel" as they fled France, he said.

According to Le Parisien, French investigators say Daillet may also have encouraged a vehicle ramming attack on a police station in Dax, southwestern France, in November.

Last summer, they say he used a fake social media account to praise vandals who defaced a prominent Nazi massacre memorial at Oradour-sur-Glane, with slogans denying the Holocaust.

Mia's mother had lost custody of her daughter and was no longer allowed to see her alone or speak with her on the telephone.

Hundreds of police were mobilised in the search, which ended on Sunday morning at a squat inside an abandoned factory in the Swiss municipality of Sainte-Croix.

Mia was returned to her grandmother's care on Monday, while Lola Montemaggi remains in Swiss custody while awaiting extradition.