Credit Suisse, one of Switzerland's biggest banks, said on Tuesday that it expects to pay a $536m (€368.2m) penalty as part of a continuing US investigation into how major western banks illegally handled funds for Iran.

Credit Suisse's role in alleged illegal transactions with Iranian enterprises previously had been disclosed. But the size of the fine and the fact that the Swiss bank joins other banking companies in settling US enquiries highlight how far-reaching and secretive money flows have been with Iran and others sanctioned by the US.