German magazine Der Spiegel reported Sunday that Israel and at least one other intelligence agency listened in on U.S. Secretary of State John Kerry's unsecured phone calls last year when he was holding peace negotiations with various Middle East leaders.

The magazine cited "several sources from intelligence circles" as saying that although Kerry has a secure phone at his mansion in Georgetown, while he was traveling and needed to make a quick phone call, he sometimes used an ordinary telephone that the intelligence agencies listened in on.

"A large number of these conversations, which went via satellite, were listened to by at least two intelligence agencies, including the Israelis," the magazine wrote. "It is probable that the Russians and Chinese were also listening in."

The magazine said Israel thus often knew what Kerry was talking to the other sides about. Kerry, the magazine said, was aware of the risks but wanted results and personal conversations were more important to him than concerns from his security advisers.

The magazine said Israel and the U.S. had no comment on the report.