Iran has warned that it will react to Saturday’s Israeli airstrikes with a “proportional response”, according to sources cited in Iran’s semi-official news agency Tasmin.

“Iran reserves the right to respond to any aggression, and there is no doubt that Israel will face a proportional reaction for any action it takes,” Tasmin quotes the sources as saying.

This comes after Israel launched retaliatory airstrikes on military sites in Tehran, Karaj, Isfahan and Shiraz in the early hours of Saturday, targeting drone and ballistic missile manufacturing and launch sites, as well as air defence batteries.

The IDF said it hit around 20 targets in the “precise” operation, responding to Iran's barrage of almost 200 ballistic missiles on Israel earlier in October. Iran’s army said that Saturday’s attack killed four soldiers, two “while battling projectiles”. It said the country’s air defence had “successfully intercepted” the strikes, but that “some areas sustained limited damage”.

The Iranian Foreign Ministry condemned Israel’s attack, calling it a “blatant violation” of international law.

“The Islamic Republic of Iran considers itself entitled and obliged to defend itself against foreign acts of aggression," it said, citing Article 51 of the United Nations Charter.

Iran’s supreme leader said it is up to Iranian officials to determine how best to demonstrate Iran’s power to Israel. "It is up to the authorities to determine how to convey the power and will of the Iranian people to the Israeli regime and to take actions that serve the interests of this nation and country,” the IRNA news agency cited Ayatollah Ali Khamenei as saying.

"The evil committed by the Zionist regime (Israel) two nights ago should neither be downplayed nor exaggerated", he said.

“The miscalculations of the Israeli regime must be disrupted. It is essential to make them understand the strength, will, and initiative of the Iranian nation and its youth.”

According to news site Axios, Israel sent a message to Iran ahead of its attack through third parties, warning Iranians not to respond in an attempt to prevent an escalation into all-out war. Axios reported that the Israelis made it clear to the Iranians in advance what they were planning to attack, and what they were not planning to attack. Israel is said to have stressed that “if Iran does retaliate, Israel would conduct another more significant attack, especially if Israeli civilians are killed or injured.”

One of the channels for communicating messages to Iran was Dutch Foreign Minister Caspar Veldcamp, Axios reported.

"I spoke with the Iranian Foreign Minister about war and the heightened tensions in the region. Regarding the latter, I urged for restraint. All parties must work to prevent further escalation," Veldcamp wrote on X hours before the Israeli attack.

The US did not participate in the airstrikes, but the White House was notified shortly before, a spokesperson said, and President Joe Biden was  reported to be following developments closely.

The official described Israel’s attack as “extensive and “precise”. “The effect was a proportionate self-defence response. The effect is to deter future attacks and to degrade Iran’s abilities to launch future attacks.”

The official stressed that “this be the end of the direct military exchange between Israel and Iran”.

In a phone call with Israel Defence Minister Yoav Gallant on Saturday, US Secretary of Defence Lloyd Austin emphasised Washington’s “ironclad commitment to Israel’s security and support for its right to defend itself,” just like he did after Iran’s ballistic missile attack on Israel on October 1, according to Maj. Gen. Pat Ryder, the Pentagon press secretary.

Speaking after Israel’s attack, Austin cited America’s “recent deployment of a Terminal High-Altitude Area Defence battery to Israel”, as evidence of its commitments to the country, according to Ryder.

Austin said that the United States was “determined to prevent any actor from exploiting tensions or expanding the conflict in the region,” and told minister that “Iran should not make the mistake of responding to Israel’s strikes, which should mark the end of this exchange.”

Austin also discussed “the opportunities that now exist to use diplomacy to dial down tensions in the region, including a hostage release and ceasefire deal in Gaza and an agreement in Lebanon that allows civilians on both sides of the Blue Line to return safely to their homes,” according to Ryder.

Israel reportedly sent a message to Iran ahead of its attack through third parties, warning Iranians not to respond in an attempt to prevent an escalation into all-out war.

One of the channels for communicating messages to Iran was Dutch Foreign Minister Caspar Veldcamp, according to news site Axios.

"I spoke with the Iranian Foreign Minister about war and the heightened tensions in the region. Regarding the latter, I urged for restraint. All parties must work to prevent further escalation," Veldcamp wrote on X hours before the Israeli attack.