Israel on Tuesday vowed that "there will be repercussions" after Iran unleashed a barrage of nearly 200 missiles into Israel.
Daniel Hagari, a spokesman for the Israel Defence Forces, said the Israeli military had “plans” to respond to the attack amid growing fears of a wider conflict in the region.
Israeli Prime Minister Benjamin Netanyahu vowed to retaliate, warning Iran it "made a big mistake tonight and it will pay for it."
Israeli authorities said there were no serious injuries following the attack on Tuesday evening, though some missiles managed to land. The extent of damage remained unclear.
Alarms sounded across Israel and explosions could be heard in Jerusalem and the Jordan River valley after Israelis piled into bomb shelters.
Hundreds of flashes could be seen over the cities of Tel Aviv, Ashdod and Jerusalem as the Iron Dome system air defence system attempted to intercept the Iranian ballistic missiles.
The attack came after Israel said ground troops crossed into Lebanon on Monday night, launching what the military described as a limited operation to root out Hezbollah fighters and infrastructure.
Rear Admiral Hagari said: "There will be repercussions to this attack. We have plans.
"For now we are not identifying more attacks. We will operate at the time and place we decide."
US National Security Adviser Jake Sullivan condemned the attack, which he called a “major escalation”.
“It is equally significant that we were able to step up with Israel and create a situation in which no one was killed in this attack in Israel," he told reporters at the White House.
"We have made clear that there will be consequences, severe consequences, for this attack, and we will work with Israel to make that the case.”
Iran said the missiles were in response to the killing of Hezbollah leader Hassan Nasrallah and Revolutionary Guard General Abbas Nilforushan, both killed in an Israeli airstrike last week in Beirut.
Iran’s Islamic Revolutionary Guard Corps said its forces used hypersonic missiles for the first time and claimed that 90% of projectiles hit their targets. IRGC sources told state media in Tehran that it had targeted three Israeli military bases in the attack.
A Israeli military spokesperson said Israel recorded "a few hits in the centre and other areas in the south of the country but "a large number" of the missiles fired by Iran were intercepted by its air defences.
UK Prime Minister Sir Keir Starmer said he "completely condemned" Iran's actions and called for de-escalation across the region.
“We stand with Israel and we recognise her right to self defence in the face of this aggression,” he said in a statement in Downing Street.
“Iran must stop these attacks. Together with its proxies like Hezbollah, Iran has menaced the Middle East for far too long, chaos and destruction brought not just to Israel, but to the people they live amongst in Lebanon and beyond.”
He warned he was "deeply concerned that the region is on the brink and I am deeply concerned about the risk of miscalculation".
Ebrahim Azizi, the head of Iranian Parliament’s National Security and Foreign Policy Committee, said on Iranian state TV that this was his country’s first wave of attacks.
He said Israeli “military centres and facilities were our targets, but the attacks might have lead to civilians being hit as well due to possible miscalculations”, the BBC reported.
In a post on X, Iranian president Masoud Pezeshkian warned Mr Netanyahu "should understand that Iran is not warlike, but it will stand firmly against any threat".
"This is only a glimpse of our capabilities," he continued. "Do not engage in conflict with Iran."
Mr Netanyahu told Israelis in a video statement: “We are in the midst of a campaign against Iran's axis of evil.
“Together we will stand steadfast in the trying days ahead of us. Together we will stand. Together we will fight and together we will win."
It comes after Israel announced it is carrying out “limited” and “targeted” ground raids on Hezbollah in Lebanon.
The Israeli military said operations in Lebanon began on Monday night and involved paratroops and commandos from the elite 98th division, which was deployed to the northern front two weeks ago from Gaza where they had been fighting for months.
Over 1,000 people have been killed in strikes on Lebanon in the past two weeks, nearly a quarter of them women and children, according to the Health Ministry.
Hezbollah began firing rockets into Israel almost a year ago, in support of its ally Hamas in the war in Gaza, which began after the militant group staged the deadliest assault in Israel's history on October 7.
