Prince Victor Emmanuel, the son of Italy's last king, has been arrested as part of an investigation into corruption and prostitution.
Victor Emmanuel's return to Italy ended 56 years of family exile
The 69-year-old was held in the northern Italian city of Lecco in connection with the recruitment of prostitutes for clients at a casino.
The prince's family have vigorously denied the allegations.
Victor Emmanuel returned to Italy in 2003, 56 years after the House of Savoy went into exile.
The prince was arrested as part of an investigation by magistrates based in the southern city of Potenza.
Italian reports say he is being questioned on allegations of corruption and forgery.
Investigators reportedly suspect the prince of having contacts with the Mafia, and playing some role in the hiring of prostitutes for the clients of a casino in Campione D'Italia, the Italian enclave in Switzerland.
Speaking on Italian television, the prince's son, Emmanuel Filiberto, said he was "stunned", calling his father's arrest "yet another publicity stunt".
"I hope [the prosecutor] is sure of his charges, or it will be the last time he does anything,"he was quoted by AFP news agency as saying.
"They took him [and] they removed his mobile phone... They treated him like a bandit."
Victor Emmanuel is the son of King Umberto II, who was forced into exile after World War II as punishment for the support offered by his father King Victor Emmanuel III to the Fascist dictator Benito Mussolini.