Israeli jets carried out air strikes in Iran in the early morning hours of Saturday local time and its forces said "precise strikes" on military sites were retaliation for an October 1 Iranian ballistic missile attack on Israel.
The move brings the Mideast closer to all-out war between two of its strongest military powers, as combat pitting the Jewish state against Iran-backed Lebanese Hezbollah and Palestinian Hamas has ratcheted up in recent weeks.
Multiple explosions were heard in and around the capital Tehran at around 2:15 am local time. Official news agencies said no casualties were yet reported.
The Israeli military signaled that the strikes would be limited to military sites but the country was prepared for any escalation.
"In response to months of continuous attacks from the regime in Iran against the State of Israel – right now the Israel Defense Forces is conducting precise strikes on military targets in Iran," Israeli military Spokesperson Rear Admiral Daniel Hagari said in a video recording posted on X.
"Our defensive and offensive capabilities are fully mobilized," he added.
The United States, Israeli's main political and military backer, described the attack on their mutual archenemy in the region as self-defense.
"We understand that Israel is conducting targeted strikes against military targets in Iran as an exercise of self-defense and in response to Iran’s ballistic missile attack against Israel", he said in statement.
Jonathan Harounoff, International Spokesperson for Israel at the United Nations told Iran International Israel had to respond to Iran's missile barrage.
"Israel has a right and a duty to defend itself from a regime that has continued to attack Israel relentlessly over the past year, directly and through its terror proxies," he said.
That attack came in response to Israel's likely assassination of Hamas leader Ismail Haniyeh in Tehran in July and killing of Hezbollah chief Hassan Nasrallah last month.
It was the second direct attack by the Islamic Republic on Israel this year after an earlier salvo in April which also caused minimal damage or casualties and was repelled with US help.
Israel's strike on Iran is unfolding in multiple stages, with a second wave starting around 5 in the morning, according to the Wall Street Journal, citing a US official.
Blasts were also heard in the southwestern cities of Ahvaz and Abadan in Khuzestan province, residents told Iran International during the apparent second wave.
Mizan News agency in Iran reports new sounds of explosions heard Tehran.
The second wave hit Parchin, a very large area of military factories for missiles and drones, according to Beni Sabit, an expert on Iran from the Israeli National Security and Strategy Institute (INSS).
He used to serve as a Persian spokesperson for the Israeli government on Iranian issues and is in contact with senior Israeli officials.
"The United States is not participating in this Israeli military operation," a US senior administration official told Iran International.
Israel's attacks in Iran had ended by about 5 AM Israeli time after hitting around 20 sites during the night, the New York Times reported citing two Israeli officials.