UBS said the Swiss federal tax administration (FTA) had demanded that it provide information about former and current clients living in France, based on data from 2006 to 2008, following a French request for international administrative assistance.
"Pursuant to the disclosure order, UBS is required to produce the requested information to the FTA," the bank said in a statement, adding though that it had "expressed its concerns to the FTA that the legal grounds for this request are ambiguous at best".
UBS said that it had taken measures to inform affected clients, but stressed that many of the accounts affected by the French request have been closed.
The bank said the French request was based on data received from the Germany authorities, who have previously conducted a range of tax probes involving Swiss banks.
"Certain data related to UBS clients booked in Switzerland was seized during these investigations and also apparently shared with other European countries," UBS said, adding that it "expects other countries to file similar requests."
Tuesday's announcement came after French finance prosecutors last week asked for UBS to face trial for allegedly orchestrating a vast system of tax fraud in France, according to a legal source.
France opened a probe into UBS after former employees blew the whistle over the bank's alleged system of setting up dual accounts to hide the movement of capital into Switzerland between 2004 and 2012.
UBS denies the accusations, arguing that its involvement in such financial operations has not been proven.
Meanwhile, the documents Germany handed to French judges last year allowed them to evaluate the assets of French clients held by the bank in 2008 at nearly 12 billion euros, according to a source close to the investigation.
However not all involved tax evasion.
UBS has been embroiled in a whole series of similar cases, most notably in the United States where the authorities said the bank used Switzerland's banking secrecy laws to help rich clients avoid the taxman.