Customers of Valartis, a Chinese-owned Liechenstein bank, are being told by unknown blackmailers they must pay 10% of their life savings or face having account details sent to finance authorities and the media, German-language newspaper Bild reports.
On Tuesday, the bank said that it did not know of any money losses, and that account statement was not obtained.
"The attacker did not obtain details of the account statement or asset data," Chief Financial Officer Fong Chi Wah said in the statement. "Possible affected customers have already been informed by the bank."
The attacker obtained unauthorized access to the bank's e-banking system and obtained information on payment orders, parent company Citychamp said.
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. Valartis Bank Liechtenstein is located in the tiny Alpine principality sandwiched between Austria and Switzerland.
Trade in Citychamp's Hong Kong-listed shares slumped as much as 12 percent in thin trade on Tuesday morning after being suspended on Monday.
Unknown hackers found their way into the Liechtenstein bank's system and obtained customer account information, including that of many Germans - with politicians, actors, and high net worth individuals among Valartis Liechtenstein's customers.
The hackers are reportedly demanding 10 percent of the account balances, to be paid in bitcoin - an internet currency favoured by criminals because of its anonymity - before December 7.
According to The Register, the unidentified attackers allege that releasing the information will reveal evidence of tax evasion.