By Inti Landauro in Paris and John Letzing in Zurich 

French prosecutors on Friday said they are investigating the Swiss unit of HSBC Holdings PLC for allegedly laundering the proceeds of tax fraud, marking the latest international probe into the aiding of offshore-tax evasion by Swiss banks.

Magistrates are also looking into whether the bank sought to recruit customers in France, possibly breaching laws authorizing only French-registered lenders to sign up customers in the country, an official at the office of the French national financial prosecutor said.

In a statement, HSBC's Swiss bank said French magistrates are examining whether it "acted appropriately" in the years 2006 and 2007 in relation to French taxpayers, "as well as in relation to the way the bank offered its services in the country."

The bank said it has been asked to deposit a bond of EUR50 million ($62 million) in relation to the probe, and said it will cooperate "to the fullest extent possible."

A spokeswoman for the bank declined to comment further.

The disclosure Friday followed formal charges filed earlier in the week by a Belgian judge, alleging that HSBC's Swiss bank helped Belgians evade taxes by harboring funds in secret accounts. The misconduct alleged in Belgium occurred between 2003 and the present, according to the Brussels prosecutor's office. The bank said at that time the Belgian charges were disclosed that they were linked to a probe by French authorities.

In addition, HSBC's Swiss unit is one of about a dozen Swiss banks that remain under criminal investigation by the U.S. Justice Department for allegedly aiding American tax evasion with secret Swiss accounts.

Zurich-based Credit Suisse Group AG settled its own, related probe earlier this year by agreeing to pay $2.6 billion.

Write to Inti Landauro at inti.landauro@wsj.com and John Letzing at john.letzing@wsj.com

Access Investor Kit for HSBC Holdings Plc

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=GB0005405286

Access Investor Kit for HSBC Holdings Plc

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=US4042804066

Subscribe to WSJ: http://online.wsj.com?mod=djnwires