U.S. Secretary of Defense Chuck Hagel said on Thursday he heard the reports about Israeli spying on the U.S. and that he was unaware of evidence supporting such claims.

Asked during a press conference in Tel Aviv about a Newsweek magazine story quoting unnamed U.S. officials as saying Israel was conducting major spying operations against the United States, Hagel said: "I have heard of that report. I'm not aware of any facts that would substantiate the report."

Israeli Defense Minister Moshe Ya'alon, who responded to the espionage question in English, said: "As former head of (Israeli military) intelligence, I wasn't allowed to spy in the United States whatsoever. And as defense minister I don't allow to spy in the United States whatsoever."

Israeli officials had reacted furiously to the Newsweek story, with Foreign Minister Avigdor Lieberman calling it "malicious."

Ya'alon, who has this year criticized U.S. foreign policymaking, and Hagel both affirmed the strong bond between Israel and the United States, and Hagel noted the record levels of U.S. aid to Israel.

The U.S. defense chief is on a three-day visit to Israel, where he was due to discuss a host of issues, from Iran to Syria to the failed Palestinian peace process.