TEHRAN, Iran (AP) -- Tehran is not surprised by reports that a cyber-espionage campaign targeted hotels that hosted nuclear talks between Iran and world powers, Iran's envoy to the U.N. nuclear watchdog agency said Thursday.

Reza Najafi told Iran's state TV that Iranian nuclear negotiators took "precautionary measures" to protect their secrets.

His remarks were the first from Tehran after Kaspersky, a cybersecurity firm with close ties to Russian intelligence, said Wednesday the malware it had uncovered at the hotels was so sophisticated that it must have been created by a government.

Citing former U.S. intelligence officials, The Wall Street Journal attributed the spying to Israel, which opposes the emerging nuclear deal between Iran and world powers. The Israeli government declined comment Wednesday.

Najafi also appeared to put the blame on Israel.

"These talks have enemies, especially the Zionist regime, which doesn't want the negotiations to succeed," said Najafi, referring to Israel. "They won't spare any efforts" to undermine the talks.

"We are not surprised by the issue of espionage," he said, adding that Iran is always careful to protect its secrets - irrespective of efforts by Israel and others to spy on them.

"Iran's negotiators have taken and are taking all the precautionary measures during the negotiations," he was also quoted as saying.

The spy allegations coincide with deepening tensions in the U.S.-Israeli relationship, much of it linked to Iran. The Obama administration has rejected much of the hawkish advice of its close Mideast ally in favor of what U.S. officials say would be an accord that removes the threat of a nuclear-armed Iran. The Jewish state has aggressively lobbied against the emerging agreement both internationally and within the United States.

Israeli Prime Minister Benjamin Netanyahu's office had no comment on the espionage allegations. But earlier Thursday, Tzipi Hotovely, Israel's deputy foreign minister, denied involvement.

Negotiators from the six-nation group - United States, Russia, Britain, France, China and Germany - and Iran hope to clinch a final accord by the end of the month to curb Iran's nuclear activity for a decade in exchange for lifting sanctions.

The six powers want long-term caps on Iranian nuclear programs that could be used to make weapons. Tehran denies any interest in atomic arms and is seeking an end to sanctions in exchange for nuclear concessions.

Switzerland and Austria are investigating the allegations of spying at the nuclear talks.

By The Associated Press