Societe Generale confirmed the searches, declining further comment. The other banks concerned did not immediately reply to requests for comment.

The PNF financial prosecution office said in a statement the probe was linked to so-called "cum-ex" dividend stripping, a trading scheme whereby banks and investors swiftly trade shares of companies around their dividend payout day.

The practice aims blur stock ownership and allow multiple parties to illegally reclaim tax rebates on dividends.

The PNF, confirming an earlier report in newspaper Le Monde, said Tuesday's searches had also targeted Exane, which is a unit of BNP, and Natixis, the investment bank arm of French banking group BPCE.

The searches by French prosecutors are the latest to hit global banks as similar investigations have been conducted in other European countries, including Germany.

A German court in December sentenced tax lawyer Hanno Berger, alleged to have masterminded one of the country's biggest post-war frauds through a dividend-stripping scheme that some estimates said cost German taxpayers around 10 billion euros, to eight years in jail.

It was the highest-profile prosecution and longest sentence to date in a series of trials that have also convicted British bankers.

"The ongoing operations, which have required several months of preparation, are being carried out by 16 investigating judges and over 150 investigation agents," the PNF said in its statement. It said six German prosecutors were also assisting the investigations.

The searches come as the global banking sector is in turmoil following this month's collapse in the United States of Silicon Valley Bank and Signature Bank, and the government-orchestrated takeover of Credit Suisse by rival UBS.

(Reporting by Tassilo Hummel, Blandine Hénault and Sudip Kar-Gupta; writing by Silvia Aloisi, Editing by Giles Elgood)