Switzerland’s Attorney General said on Wednesday that authorities have searched multiple premises in relation to an investigation into allegations that hackers had targeted venues which hosted negotiations on Iran's nuclear program, Reuters reports.

"We have an open investigation into political espionage in Switzerland," Attorney General Michael Lauber was quoted as having told a news conference.

His office was analyzing data acquired during the searches, he added. An aide said the premises searched were hotels.

The Wall Street Journal reported last week, citing the Russian computer security company Kaspersky Lab, that Israel attempted to use a sophisticated virus to spy on nuclear talks between Iran and P5+1 by hacking into the servers of hotels where talks were being held.

Israel vehemently denied the report, with Deputy Defense Minister Rabbi Eli Ben-Dahan calling the allegations “utter nonsense”. The U.S. State Department said on Thursday it was confident there had been no security breach in the talks.

Kaspersky said it had found the software in three European hotels. The suspected virus infections were linked to events and venues related to the negotiations between six world powers and Iran on curbing Tehran's nuclear program.

Lauber declined to comment on who might be involved in the hacking, according to Reuters.

Iran originally said it was not surprised by the reports of the virus and claimed it had taken all the necessary precautions, but the next day it said it was “concerned” over the security of the talks.