Swiss prosecutors say they are conducting an espionage investigation amid suspicions that Swiss hotels hosting talks on Iran's nuclear program have been targeted in a cyber-spying campaign.

Kaspersky, a cybersecurity firm, said this week it uncovered the campaign and that the malware was so sophisticated it must have been created by a government.

Andre Marty, a spokesman for Swiss federal prosecutors, said Thursday that Switzerland's investigation is directed against persons unknown and was opened following a report from the Swiss intelligence agency. He said in an emailed response that a search took place in Geneva on May 12 during which unspecified information technology material was seized.

Most of the Iran talks over recent months have taken place in Switzerland and Austria.