Swiss lender Zuercher Kantonalbank (ZKB) said two of its bankers and one former employee had been charged by U.S. authorities, which had accused them of helping U.S. clients avoid taxes.
The three were indicted over changes of conspiring with American clients to hide more than $420 million from the U.S. Internal Revenue Service, the U.S. Attorney's Office in Manhattan had said on Wednesday.
The indictment did not identify the bank concerned but named Stephan Fellmann, Otto Hueppi and Christof Reist, who it said were all former client advisers for the unnamed institution.
None of the bankers had been arrested, authorities said.
Banking secrecy is enshrined in Swiss law and tradition but has recently come under pressure as the United States and other nations have moved aggressively to tighten tax law enforcement and demand more openness and cooperation.
U.S. authorities are investigating at least 11 banks, including Julius Baer, Credit Suisse and other Swiss regional banks, along with UK-based HSBC Holdings and Israel's Hapoalim, Mizrahi-Tefahot Bank Ltd and Bank Leumi.
In February, Wegelin & Co, Switzerland's oldest private bank, was indicted.
UBS AG, the largest Swiss bank, in 2009 paid a $780 million fine as part of a settlement with U.S. authorities who charged the bank helped thousands of wealthy Americans hide billions of dollars in assets in secret Swiss accounts.
ZKB said in a statement it was cooperating with U.S. authorities. The bank said it could give no details about the employees due to the ongoing investigation and did not confirm what they had been changed with.
ZKB bankers Fellmann and Reist could not be reached for comment. Hueppi declined to comment.
(Additional reporting by Caroline Copley and Martin de Sa'Pinto; Editing by Phil Berlowitz and David Holmes)