Shares in UBS were indicated to open down 2.2 percent on Friday after U.S. tax authorities said they were seeking 52,000 bank client names even though the Swiss bank has agreed to a hefty fine to settle criminal charges.

The stock was seen down at 12.52 Swiss francs, premarket data provided by bank Clariden Leu showed, reversing some of Thursday's strong gains.

Analysts had welcomed a settlement late on Wednesday in the hope it would take the U.S. tax probe into helping rich Americans dodge tax off the table and allow UBS to focus on a badly-needed restructuring.

But the civil U.S. lawsuit announced late on Thursday will continue to keep UBS under pressure and will be watched by the whole $7-trillion offshore banking industry as it could open further cracks in closely-guarded bank secrecy rules that helped the sector thrive.