“As is the case wherever we operate, Pictet has made it a priority to ensure that its business with US clients complies with all the relevant laws and regulations governing its conduct as part of our professional responsibility towards our clients, counterparties, supervisors, and the public,” the bank said in a statement. 

The statement did not elaborate on the exact nature of the US enquiries, nor the precise nature of any investigation under way. The US Department of Justice could not be reached outside of US business hours for comment at the time of going to press.

Pictet said it will cooperate “as fully as possible” with the US authorities.

"We look forward to demonstrating this commitment to the US Department of Justice and to cooperating as fully as possible with them," Pictet's statement added. 

A number of Swiss banks, led by UBS, the country’s biggest bank, no longer provide offshore financial services to US citizens. In 2009, UBS reached settlements over criminal and civil charges that it aided wealthy Americans to avoid tax; it has also agreed to hand over some client account details to US authorities. There have been probes of other foreign banks by the US authorities as the country seeks to crack down on offshore tax evasion.