Shares in UBS AG are down after reports the Swiss bank could face a fine of 4.88 billion euros ($6.16 billion) if found guilty of facilitating tax evasion and money laundering in France.

Geneva daily Le Temps on Friday cited prosecution documents obtained by French investigative news site mediapart.fr that put the potential penalty for UBS significantly higher than a 1.1 billion euro bond it has had to deposit in the case.

The bank, which has denied allegations it helped rich French clients dodge taxes, called the publication of the documents "irresponsible" and repeated its stance that "the base for any calculations in this matter are completely artificial, speculative and not based on facts."

UBS shares were down 1.4 percent at 16.09 Swiss francs ($16.80).