Israel said it conducted air strikes against Iran on Saturday that hit military bases and missile sites in retaliation for the Islamic republic's attacks, warning it would "pay a heavy price" if it responds.
The Israeli military said its strikes hit Iran's missile manufacturing facilities, missile arrays and other systems in several regions.
Iran confirmed an Israeli attack had targeted military sites in the capital Tehran and other parts of the country, but said it had caused "limited damage".
Israel had vowed to hit back at Iran for its October 1 missile strike, the second-ever direct attack by the Islamic republic on its arch-foe.
The rapid escalation of violence has heightened fears across the region and beyond of a wider war, pitting Israel against Iran and the allies it dubs the "axis of resistance" on multiple fronts.
"Based on intelligence, IAF (air force) aircraft struck missile manufacturing facilities used to produce the missiles that Iran fired at the State of Israel over the last year," Israel's military said in a statement.
"Simultaneously, the IDF (military) struck surface-to-air missile arrays and additional Iranian aerial capabilities," the army said, adding that the "retaliatory strike has been completed and the mission was fulfilled".
Since the deadliest attack in its history on October 7, 2023, Israel has been fighting Hamas in Gaza, and since late last month, it has been at war with Hezbollah in Lebanon.
Both Hezbollah and Hamas are allies of Iran, as are armed groups in Yemen and Iraq and the government in Syria.
In a statement announcing the operation, the Israeli military said it was conducting "precise strikes on military targets in Iran", in response to what it said were "months of continuous attacks from the regime in Iran".
"The regime in Iran and its proxies in the region have been relentlessly attacking Israel since October 7th -- on seven fronts -- including direct attacks from Iranian soil," the military said.
Iran on Saturday suspended all flights until further notice, the aviation authority announced.
Iran in April launched its first-ever direct assault on Israeli territory in retaliation for a deadly strike on Iran's consular annex in Damascus.
Hamas's October 7, 2023, attack on Israel that sparked the war in Gaza killed 1,206 people, mostly civilians, according to an AFP tally of official Israeli figures.
Israel's retaliatory campaign in Gaza has killed 42,847 people, the majority civilians, according to figures from the Hamas-run territory's health ministry which the United Nations considers reliable.
Israel has since broadened the scope of its operations to Lebanon, vowing to secure its northern border after nearly a year of attacks launched by Iran-backed Hezbollah in support of Hamas.
At least 1,580 people have been killed in Lebanon since September 23, according to an AFP tally of Lebanese health ministry figures.
Iran's October 1 strike came after an Israeli air raid killed Hezbollah chief Hassan Nasrallah and Revolutionary Guards general Abbas Nilforoushan in Lebanon on September 27.
The killing of Nasrallah, which dealt Hezbollah a seismic blow, followed the death of Hamas political leader Ismail Haniyeh on July 31 in Iran in an attack widely blamed on Israel.
Iran's air defence force confirmed an Israeli attack had targeted several military bases in Tehran and other areas.
"This fake regime (Israel) attacked parts of military centres in Tehran, Khuzestan and Ilam provinces," it said in a statement, adding that the attack "caused limited damage" while being intercepted.
Earlier, Iranian state television reported blasts around the capital, saying they were due to the "activation of the air defence system" against an Israeli attack.
An AFP reporter in Tehran also heard explosions.
Iran had in recent weeks warned that any attack on its infrastructure would provoke an "even stronger response", while Revolutionary Guards general Rassul Sanairad said an attack on nuclear or energy sites would cross a red line.
US National Security Council spokesman Sean Savett said the "targeted strikes on military targets" are "an exercise of self-defence and in response to Iran's ballistic missile attack against Israel on October 1."
The United States was "informed beforehand and there is no US involvement," a US defence official told AFP, on condition of anonymity.
The official did not say how far in advance the United States had been informed or what had been shared by Israel.
Syrian state news agency SANA said Israel conducted an air attack on Saturday from the occupied Golan Heights and Lebanon, targeting military positions in Syria.
Citing an unnamed military source, the agency said the attack at around 2:00 am (2300 GMT) had targeted positions in central and southern Syria.
The attack prompted Syria to activate its air defences, SANA said, as Israel announced it was launching "precision strikes" in neighbouring Iran.
Iran and Syria are allies in the so-called "axis of resistance" that also includes Hezbollah in Lebanon and Hamas in Gaza.
"Our anti-aircraft defence is confronting hostile targets in the skies around Damascus," state news agency SANA reported on Telegram.
SANA had previously reported the "sounds of explosions" in the vicinity of the Syrian capital.
The Islamic Resistance in Iraq, a loose network of pro-Iran factions, claimed responsibility early Saturday for a drone attack against a "military target" in northern Israel, following the announcement of Israeli strikes on Iran.
Iraq suspended all air traffic Saturday at its airports until further notice after Israel its attack.
