US prosecutors have accused three Swiss bankers of conspiring with US taxpayers to conceal more than $1.2 billion in assets from tax authorities, and sources briefed on the matter said the persons worked for Wegelin & Co, Reuters reported.

The office of the Manhattan US Attorney said in a statement that the indictment charges the bankers with trying to "capture business lost by UBS and another large international Swiss banks in the wake of widespread news reports that the Internal Revenue Service was investigating UBS" in 2008 and 2009.

The development signals how US authorities have started the New Year in the same mood as they finished the previous one: working to crack down on alleged offshore tax evaders, particularly those using Swiss bank accounts. A number of Swiss firms, such as UBS, Julius Baer, Wegelin and Credit Suisse, no longer provide offshore banking services to US clients. The US Department of Justice is conducting criminal probes into 11 banks, either Swiss or global with major Swiss operations.

Wegelin was not identified in the single indictment filed against Michael Berlinka, Urs Frei and Roger Keller. The three men, who reside in Switzerland, worked for the unnamed clients between 2005 and 2010, and sold tax evasion services from the bank's Zurich office, the news service quoted the indictment as saying.

Wegelin does not have a US presence, and the bank carried out its work for approximately 100 US clients through a Stamford, Connecticut, branch of UBS, the giant Swiss bank, according to the indictment.

Wegelin "directly accessed the US banking system through a correspondent bank account held at UBS," which the indictment said was in Stamford, Connecticut.

If convicted, the bankers face a maximum prison term of five years under the conspiracy charge.

Swiss authorities want a global civil settlement with US authorities in which the entire Swiss banking industry would pay a fine and shut undisclosed private banking services for US citizens.