UBS, the world's largest wealth manager, unveiled $3.4 billion in losses, swept out senior managers and slashed jobs in one of the biggest casualties yet from the worldwide credit crunch.

UBS said on Monday it would write down a net 4 billion Swiss francs ($3.42 billion) in its fixed-income portfolio and elsewhere, resulting in a third-quarter loss of 600 million to 800 million Swiss francs, its first quarterly loss in nine years.