Israel launched multiple air strikes on Iran in the early hours of Saturday, in response to what the Israeli military called "months of continuous attacks" from Tehran and its proxies.
The Israel Defense Forces (IDF) says it is carrying out "precise strikes on military targets" in Iran, which it accuses of "relentlessly attacking Israel" since 7 October 2023.
The IDF's confirmation of strikes on Iran followed earlier reports by Iranian state media of several explosions in and around the capital, Tehran.
It comes after Tehran launched almost 200 ballistic missiles towards Israel on 1 October, in what the country said was a retaliation for the killing of Hamas's political leader on Iranian soil back in July.
In a statement announcing that the operation in Iran was under way, the Israeli military spokesman, Daniel Hagari, said Israel had the "right and duty" to respond and its "defensive and offensive capabilities" were "fully mobilised".
The US, one of Israel's closest allies, said Saturday's strike against Israel was an "exercise of self-defence".
"We understand that Israel is conducting targeted strikes against military targets in Iran as an exercise of self-defence and in response to Iran’s ballistic missile attack against Israel on October 1," a National Security Council spokesman told the BBC's US news partner CBS.
The 1 October attacks were largely thwarted by Israel's military, but a small number struck central and southern Israel.
Tehran said it had attacked Israel in retaliation for what it called the "violation of Iran’s sovereignty and the martyrdom" of Hamas political leader Ismail Haniyeh, who was killed by an explosion in Tehran in July that Iranian officials blamed on Israel, but Israeli officials did not claim responsibility.
At the time, Iran said the attack was also in response to the Israeli air strike in the southern suburbs of Beirut that killed Hezbollah leader Hassan Nasrallah and Brig-Gen Abbas Nilforoushan, the operations commander of the IRGC’s overseas arm, the Quds Force.
That escalation came hours after Israeli troops began an invasion of southern Lebanon to remove what the military said were "Hezbollah terror targets” in border villages that posed a threat to residents of northern Israel.
Speaking after Israel launched its strikes on Saturday, a White House official said President Joe Biden "has been briefed and is closely following the developments".
However, a US defence official stressed that there had been no US involvement in the Israeli strikes on Saturday.
Iranian state media confirmed that explosions were heard in the west of Tehran. A news agency close to the Revolutionary Guards said some military bases in the west and south-west of the Iranian capital had been targeted.
The extent of the attacks and the precise targets are not yet clear.
Iranian media are denying that these attacks have caused any real damage, as reported by BBC Persian.
But the country's aviation authority announced that flights had been cancelled on all routes until further notice.
The Syrian state news agency reported that Israeli air strikes have also targeted some military sites in central and southern areas of Syria.