Israeli leaders have lashed out at Iran's top leader, Ayatollah Ali Khamenei, for describing Israel as "a rabid dog" in a speech on Wednesday.

Prime Minister Benjamin Netanyahu, who flew to Russia on Wednesday to lobby for tougher terms in the negotiations over Iran's nuclear program, said Khamenei's comments showed Iran had not changed since relative moderate Hassan Rohani was elected as president in June.

"He called Jews 'rabid dogs' and said that they were not human. The public responded to him with calls of 'Death to America! Death to Israel!' Doesn't this sound familiar to you? This is the real Iran! We are not confused," he said. 

Foreign Minister Avigdor Lieberman compared Khamenei's rhetoric to that used by Nazi Germany.

"Whoever talks about the Jews using the terminology of Goebbels and Hitler certainly has no intention to develop a nuclear program for peaceful purposes," said.

Israel is lobbying against any nuclear deal with Iran that - in its view - offers too many concessions against too few curbs on the nuclear program, and it has made clear that it does not rule out military strikes to stop Tehran from acquiring a nuclear weapon.

"They must not have nuclear weapons. And I promise you that they will not have nuclear weapons," Netanyahu told Russian Jewish community leaders in Moscow.