With Iran's clerical establishment facing the biggest anti-government protests since 2022, US President Donald Trump has repeatedly threatened to intervene in recent days, warning Iranian leaders against using force against demonstrators. On Saturday, Trump said the US stands "ready to help".
Addressing parliament on Sunday, Iranian Speaker Mohammad Baqer Qalibaf warned the US against "a miscalculation".
"Let us be clear: in the case of an attack on Iran, the occupied territories (Israel) as well as all US bases and ships will be our legitimate target," said Qalibaf, a former commander in Iran's Revolutionary Guards.
Three Israeli sources, who were present for Israeli security consultations at the weekend, said Israel was on a high alert footing, but did not elaborate on what that meant.
An Israeli government spokesperson declined to comment.
The Israeli military didn't immediately respond to a request for comment.
Israel and Iran fought a 12-day war in June, in which the US joined Israel in launching air strikes.
Iran retaliated for those US strikes by firing missiles at an American air base in Qatar.
Protests have spread across Iran since December 28, beginning in response to soaring inflation, and quickly turning political with protesters demanding an end to clerical rule.
Authorities accuse the US and Israel of fomenting unrest.
The flow of information from Iran has been hampered by an internet blackout imposed by the authorities since Thursday.
A US-based rights group, HRANA, said the death toll had climbed to 116, mostly protesters but including 37 members of the security forces.
Iranian state TV broadcast funeral processions in western Iranian cities, including Gachsaran and Yasuj, for security forces killed in protests.
A social media video posted on Saturday showed large crowds gathered in Tehran's Punak neighbourhood at night, drumming rhythmically on a bridge or other metal objects in an apparent sign of protest.
Reuters verified the location.
Iran's rulers have quelled repeated bouts of unrest, most recently in 2022 over the death in custody of a woman accused of violating dress codes.
Trump, posting on social media on Saturday, said: "Iran is looking at FREEDOM, perhaps like never before. The USA stands ready to help!!!"
In a phone call on Saturday, Israeli Prime Minister Benjamin Netanyahu and US Secretary of State Marco Rubio discussed the possibility of US intervention in Iran, according to an Israeli source who was present for the conversation.
A US official confirmed the two men spoke but did not say what topics they discussed.
A senior US intelligence official on Saturday described the situation in Iran as an "endurance game".
The opposition was trying to maintain pressure until key government figures either fled or switched sides, while the authorities were trying to sow enough fear to clear the streets without giving the US justification to intervene, the official said.
Israel has not signalled a desire to intervene, with tensions between the two arch-foes high over Israeli concerns about Iran's nuclear and ballistic missile programs.
In an interview with the Economist published on Friday, Netanyahu said there would be horrible consequences for Iran if it were to attack Israel.
"Everything else, I think we should see what is happening inside Iran," he said, alluding to the protests.
