French police rescued the father of a wealthy cryptocurrency entrepreneur in a nighttime raid after he was taken hostage for ransom, the latest alleged criminal effort in France to extort people involved in the management of digital assets.

The man was kidnapped Thursday morning in Paris, the prosecutor's office said Sunday.

"The victim turned out to be the father of a man who made his fortune in cryptocurrencies, and the incident was accompanied by a ransom demand," its statement said, without giving their names or other specifics about their identities.