The revelation comes in run-up to a June 30 deadline for a historic agreement between Iran and world powers on curtailing Tehran's nuclear programme in return for relief from punishing sanctions, and a day after a Russian-based security firm said a computer worm widely linked to Israel was used to spy on the negotiations.
Israel is vehemently opposed to a nuclear deal with Iran, with Prime Minister Benjamin Netanyahu warning that the accord would not "block Iran's path to the bomb".
The Swiss attorney general's office confirmed it had got government clearance to launch a probe into alleged spying on May 6 and conducted a raid six days later, seizing computer equipment, due to "suspicion of illegal intelligence services operating in Switzerland."
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"The aim of this raid was on one hand to gather evidence and to on the other verify if information systems had been infected by malware," the attorney general's office said in an email.
Austria -- which has also hosted numerous rounds of the nuclear talks -- said today it was also investigating possible spying at meeting venus there.
"Investigations are ongoing" regarding the Palais Coburg hotel, the location of many rounds of the talks including discussions this week, interior ministry spokesman Karl-Heinz Grundboeck told AFP.
Last month's talks in Geneva held at the luxury Intercontinental Hotel failed to bridge differences between Washington and Tehran, especially over the crucial issue of inspections of military sites.
Today's announcements came after a Russian-based security firm Kaspersky Lab said a malware dubbed Duqu, which is a sophisticated spy tool that was believed to have been eradicated in 2012, appeared to have been used to spy on the nuclear negotiations with Iran.