Customers of a Chinese-owned Liechtenstein bank are being told by unknown blackmailers they must pay a portion of their savings or face having account details sent to finance authorities and the media, a German newspaper reported.

Those targeted have accounts at Valartis Bank Liechtenstein, located in the tiny Alpine principality sandwiched between Austria and Switzerland, Bild am Sonntag reported.

A majority of the Liechtenstein bank was sold by Swiss-listed Valartis Group earlier this year to Citychamp Watch & Jewellery Group Ltd, a Hong Kong-based holding company chaired by Hon Kwok Lung.

A phone call and email to Valartis Bank Liechtenstein director Andreas Insam were not immediately returned. Citychamp also did not answer a phone call late Sunday in Hong Kong.

Valartis Group also did not return an email seeking comment.

Unknown hackers found their way into the Liechtenstein bank's system and obtained customer account information, including that of many Germans, the newspaper reported, adding politicians, actors and high net worth individuals were among Valartis Liechtenstein's customers.

The hackers are demanding 10 percent of the account balances, to be paid in Internet cryptocurrency Bitcoin to help preserve anonymity, Bild reported.