Israel is almost certain to retaliate at some stage against Iran's unprecedented drone and missile attack, but the question is how and when, say security analysts.

World leaders have urged calm and the United States, Israel's top ally, called on Israel to refrain from a military response, at a time when the region is already in turmoil over the Gaza war.

Israeli leaders have credited an international military coalition with helping thwart a direct Iranian attack involving hundreds of drones and missiles, calling the coordinated response a starting point for a "strategic alliance" of regional opposition to Tehran.

But Israel's War Cabinet met without making a decision on next steps, an official said, as a nervous world waited for any sign of further escalation of the former shadow war.

Airports in Tehran and elsewhere in Iran resumed operations Monday, state media said, after a temporary suspension due to an aerial attack on arch for Israel that heightened regional tensions.

Flights were suspended after Iran launched late Saturday its first-ever direct attack on Israeli territory, using drones and missiles, in retaliation for a deadly April 1 air strike on Tehran's consulate in Damascus which was widely attributed to Israel.

Israel and Iran accused one another Sunday at the United Nations of being the main threat to peace in the Middle East, each calling on the Security Council to impose sanctions on their sworn enemy.

"The mask is off. Iran, the number one global sponsor of terror, has exposed its true face as the destabilizer of the region and the world," Israel's U.N. Ambassador Gilad Erdan told an emergency meeting of the Security Council convened after Tehran's unprecedented attack on Israel overnight.

President Joe Biden said U.S. forces helped Israel shoot down nearly all the drones and missiles fired by Iran Saturday, but appeared to guide the key U.S. ally away from retaliating against Tehran by saying Israel had now shown its strength.

Biden added that he was convening fellow G7 leaders on Sunday to coordinate a diplomatic response against Tehran, in another sign that he is trying to avoid any further military escalation that could ignite a wider Middle East conflict.

Iran's unprecedented overnight attack on Israel has been "foiled", the Israeli military said Sunday, with hundreds of missiles and drones intercepted with the help of the United States and allies.

The attack which began late Saturday marks a major escalation of the long-running covert war between the regional foes, and comes against the backdrop of the ongoing war between Israel and Palestinian militant group Hamas in the Gaza Strip.

Countries around the world condemned Iran's strikes on Israel late Saturday, warning the attack threatened to further destabilize the Middle East.

Iran launched an unprecedented drone and missile attack on Israel, the Israeli army announced late Saturday, in a major escalation of the long-running covert war between the regional foes.

Residents have reported heavy Israeli fire in central Gaza, with regional tensions soaring after Iran threatened reprisals over a strike in Syria this month that killed two Iranian generals.

As talks for a truce and hostage release dragged on, fears that Iran could soon launch an attack on Israel prompted the United States to announce it was sending reinforcements to the Middle East as a deterrent.

Residents reported heavy Israeli fire in central Gaza on Friday, with regional tensions soaring after Iran threatened reprisals over a strike in Syria this month that killed two Iranian generals.

As ceasefire talks aiming to pause the six-month-old war dragged on, fears that Iran could soon launch an attack on Israel spurred France to recommend its citizens avoid travelling to the region.