The website of Der Spiegel magazine reported on Monday that affected customers received letters from their banks notifying them of the imminent closure of their accounts. No reason for the decision was given.
"Since November 2012 the number of complaints about blocked accounts and denied applications has risen substantially. Hundreds of Iranians have been affected," said Lutz Bucklitsch from a Berlin-based Iranian refugee organisation.
Some of the accounts had balances exceeding €1,000. Holders were notified by post that they could either withdraw the balance in cash or transfer it to another institution.
Although the banks in question have declined to reveal the reasons for their course of action, insisting on banking confidentiality, Sparkasse and Giroverband have pointed to international sanctions against Iran implemented in response to its controversial nuclear programme. The measures have drastically reduced German business ties with the country.
The sanctions have been in place since 2007 and alongside businesses they have affected particular individuals within Iran. Those who do not appear on the blacklist, however, should be allowed to continue managing their private financial affairs without hindrance.
"Due to increased pressure from trading partners in the USA, German banks have been gradually shutting Iranian customers out," Bucklitsch told Der Spiegel. "From the American point of view, no business should have anything to do with Iran."
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The rash of account closures has even reportedly sparked the German government to contact the banks. Emily Haber, a German Foreign Office official, informed the institutions by letter that their moves to block Iranian citizens' accounts had no legal basis. She has called for "a fresh audit into account management and new openings."