German state prosecutors have begun a country-wide search of premises of UBS clients on suspicion of tax evasion, Bochum state prosecutors said on Monday.
A number of state prosecutors and about 50 tax investigators were undertaking the searches of domestic German clients of UBS, Bochum state prosecutor Norbert Salamon said, adding that further action could follow.
UBS is one of several Swiss banks caught up in investigations into personal tax evasion in the United States and Europe, putting the future of Swiss banking secrecy laws in jeopardy.
Bochum prosecutors had already been carrying out an investigation based on a computer disk of data that was purchased by authorities in the state of North Rhine-Westphalia (NRW), where Bochum is located.
"UBS does not provide support to its clients for the evasion of tax obligations," a UBS spokesman said, adding that the Swiss bank had already conducted thorough checks of its business in Germany in 2009 and adjusted its rules where necessary.
NRW's finance ministry has said it has purchased six CDs of Swiss data since 2010 that point to possible German tax evaders.
UBS is also being probed by state prosecutors in the city of Mannheim over allegations of helping clients to evade tax.
The bank denied any wrongdoing in response to the Mannheim probe.
Earlier this year a number of French offices of UBS were searched as part of a probe into the alleged aiding of tax evasion.
In August UBS denied media reports it was telling wealthy Germans to move funds to Singapore and other money centres ahead of a Swiss tax deal due to come into force in January.
(Reporting by Matthias Inverardi in Duesseldorf and Oliver Hirt in Zurich; Writing by Jonathan Gould; Editing by Helen Massy-Beresford)