Israeli President Shimon Peres said on Tuesday that the threat of a nuclear-armed Iran was growing under the "terrifying dictatorship" ruling the Islamic republic.

"The Iranian danger has grown," Peres said at the opening of the newly-elected Israeli parliament. "It threatens our existence, the independence of the Arab states, the peace of the whole world.

"At its head stands a group of ayatollahs in their religious robes, a terrifying dictatorship, staining Persian history and a nightmare for its people," he said.

Much of the international community fears that Iran's nuclear programme includes efforts to develop nuclear weapons, a charge that Tehran denies.

Israel believes that Iran must be prevented from reaching military nuclear capabilities at any cost and refuses to rule out military intervention to achieve this.

It also accuses Iran of sponsoring the Lebanese militia movement Hezbollah, against which it fought a devastating war in 2006 and which Bulgaria said Tuesday was behind a July bomb attack that killed five Israeli tourists and a Bulgarian.

Addressing the opening of the 19th knesset, or parliament, elected in a January 22 general election, Peres called on the United Nations and the Arab League to act urgently to end the turmoil in Syria.

"Iran is a danger and Syria is a tragedy. Its president butchers his people. In my opinion the UN should task the Arab League with the immediate formation of a transitional government in Syria to save it from self-destruction. Assad, who has murdered tens of thousands has also murdered his future," he said.

Syria has blamed Israel for a Wednesday air raid at a military complex near Damascus, which targeted surface-to-air missiles and an adjacent military complex believed to house chemical agents, according to a US official.

Damascus has threatened to retaliate and Syria's close ally Iran warned the attack would have "grave consequences" and that the "Zionist entity" would regret its aggression against Syria

While Israel has not yet formally confirmed its responsibility, Defence Minister Ehud Barak on Sunday dropped a heavy hint.

"It's another proof that when we say something we mean it," Barak told reporters at a security conference in Germany.

"We say that we don't think that it should be allowable to bring advanced weapon systems into Lebanon, the Hezbollah, from Syria, when Assad falls."