Switzerland's stock exchange said yesterday it is investigating the loss-making banking giant UBS for possible breaches of the market's regulations.

The exchange has begun an investigation into possible breaches by UBS of a directive on publicity in 2007 and 2008, as well as rules on financial reporting "relating to corporate governance," it said in a statement.

The investigations will go on "for an indefinite period," it added, without elaborating on the probe - the latest in a series of blows for the bank which was hit hard by recent financial turmoil and a damaging US-led lawsuit.

UBS made headlines this year when US authorities accused it of aiding tax evasion by its account-holders. This led to a landmark Swiss-US agreement allowing account information to be disclosed.

US authorities also fined UBS $780 million in February in a similar tax-related case where the Swiss bank accepted full responsibility for "improper activities".

UBS was one of the hardest-hit banks as credit markets froze and stock markets slumped last year, with its future in doubt as it took massive losses.

Last month it reported an almost quadrupled net loss of 1.4 billion Swiss francs in the second quarter and warned that it needed more time to return to profitability.