There was no definitive confirmation that Credit Suisse was the main target of the fraud investigations, run by at least four European countries and Canberra and apparently involving hundreds of suspects.
The Swiss financial giant simply confirmed that its offices in London, Paris and Amsterdam had been visited by local authorities on Thursday "concerning client tax matters".
"We are cooperating with the authorities", Switzerland's number-two bank said in a statement.
Similar operations were carried out in Britain, France, Germany and Australia, all focused on clients who "deposited their money in the same Swiss bank", according to a statement from the National Prosecutor's Office for Serious Fraud, Environmental Crime and Asset Confiscation (FIOD).
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Two people accused of not declaring their savings have been arrested and two other suspects were interrogated, the FIOD said.
"Properties, and jewellery, an expensive car, expensive paintings and a gold bar", were seized from houses in The Hague and three other areas, the Dutch statement added.
"The first phase of the investigation, which will see further, targeted, activity over the coming weeks, is focused on senior employees from within the institution, along with a number of its customers," the statement from London said.
It also made no mention of Credit Suisse, but said the investigation should serve as a stark reminder to institutions that aim to help clients evade tax.
Would-be tax cheats "need to wake up to reality and accept that attempting to hide wealth overseas, or within institutions, doesn't work."
The financial fraud office said it had identified several thousands of accounts in Switzerland that were allegedly used to hide money.
This amounted to suspected "aggravated dissimulation of tax fraud", it said, with no reference to Credit Suisse.