Most of the thousands of rich people whose UBS bank accounts are to be handed over to U.S. authorities are suspected of serious fraud rather than simple tax evasion, Swiss authorities revealed on Tuesday.

The account details of about 4,450 people are due to be handed over to settle a bitter row over bank secrecy under a deal struck with the United States in August.

The saga has dented Switzerland's reputation as a center of banking discretion and threatened at one point to bring UBS to its knees.

The Swiss Justice Department said around 4,200 of the accounts are to be handed over on the grounds of advanced and serious fraud. The category covers accounts with assets of at least 1 million Swiss francs ($986,200) and 100,000 francs in average revenues over at least three years, the Swiss Justice Department said.

About a further 250 accounts are suspected of a lesser offence -- of knowingly providing U.S. tax authorities with false information or setting up vehicles to dodge tax.

The submission of information on clients suspected of dodging U.S. taxes by stashing away money in secret accounts, promises to end years of investigation and uncertainty for UBS.

Submission of data to U.S. authorities applies to UBS accounts held between 2001 and 2008 by U.S. citizens resident in the United States.

Switzerland has claimed its banking secrecy remains intact, but some private bankers say it is no longer a selling point for its banks, which will need to offer other skills like wealth management and legacy planning to attract clients.

The country will also hand over the names of U.S. citizens holding offshore company accounts with UBS if they are suspected of tax fraud or similar, regardless of whether they were resident in the U.S. or elsewhere.

Earlier on Tuesday, UBS set an ambitious target for annual pretax profit of $15 billion, vowing to rebuild the loss-making bank and win back clients after the subprime crisis and U.S. tax row.

(Editing by Erica Billingham and Andrew Callus)