Bloomberg News said that range was provided last Friday by two unnamed sources "familiar with the matter." It represents more than 10 percent of the investment banking division, which caused the bulk of UBS's $38 billion in write-downs over the past three quarters.

Overall, the biggest Swiss bank may slash as many as 8,000 jobs, close to 10 percent of its worldwide work force of 83,000, Bloomberg says. It quotes a number of European analysts who follow UBS describing the estimate - floated in media reports since mid-March - as reasonable or even conservative.

The bank is scaling back positions and giving up off-balance sheet units, said Dirk Becker, an analyst with Frankfurt-based Landsbanki Kepler who is bearish on UBS. He called the 8,000 layoffs prediction "realistic."

The reports draw on comments by Chief Executive Officer Marcel Rohner and new Chairman Peter Kurer at the UBS annual meeting in April. They said the securities unit will shrink as the company focuses on holding its ground in wealth management, UBS's traditionally dominant business franchise.

Shareholders last month approved management's request to raise 15 billion francs ($14.2 billion at Monday's exchange rate) in a rights offering. At the same time, however, a shareholder group is pressuring management to not just slim down the loss-plagued investment bank, but to separate it from the rest of the company.