Israel said it struck a nuclear site near Tehran on Wednesday, while Iran said it fired hypersonic missiles as the arch foes traded fire for a sixth day.
Hours after US President Donald Trump demanded Iran's surrender, supreme leader Ayatollah Ali Khamenei vowed his country would show "no mercy" towards Israel's leadership.
Trump insists the United States has played no part in ally Israel's bombing campaign, but also warned his patience was wearing thin.
The long-range blitz began Friday, when Israel launched a massive bombing campaign that prompted Iran to respond with missiles and drones.
After the Israeli military issued a warning for civilians to leave one district of Tehran for their safety, Israeli warplanes hit the capital early Wednesday.
"More than 50 Israeli Air Force fighter jets... carried out a series of air strikes in the Tehran area over the past few hours," the Israeli military said, adding that several weapons manufacturing facilities were hit.
"As part of the broad effort to disrupt Iran's nuclear weapons development programme, a centrifuge production facility in Tehran was targeted."
Centrifuges are vital for uranium enrichment, the sensitive process that can produce fuel for nuclear reactors or, in highly extended form, the core of a nuclear reactor.
Iran's Revolutionary Guards said they had launched hypersonic Fattah-1 missiles at Tel Aviv.
"The 11th wave of the proud Operation Honest Promise 3 using Fattah-1 missiles" was carried out, the Guards said in a statement broadcast on state television.
Hypersonic missiles travel at more than five times the speed of sound and can manoeuvre mid-flight, making them harder to track and intercept.
No missile struck Tel Aviv overnight, despite Iran's claims that its attacks were "repeatedly shaking the shelters", though AFP photos showed Israel's air defence systems activated to intercept missiles over the commercial hub.
Iran also sent a "swarm of drones" towards Israel, while the Israeli military said it had intercepted a total of 10 drones launched from Iran.
It said one of its own drones had been shot down over Iran.
- 'Unconditional surrender' -
Trump fuelled speculation about US intervention when he made a hasty exit from the G7 summit in Canada, where the leaders of the club of wealthy democracies called for de-escalation but backed Israel's "right to defend itself".
Back in Washington on Tuesday, Trump demanded the Islamic republic's "unconditional surrender".
He also boasted that the United States could easily assassinate Iran's supreme leader Ayatollah Ali Khamenei.
"We know exactly where the so-called 'Supreme Leader' is hiding. He is an easy target, but is safe there -- We are not going to take him out (kill!), at least not for now," Trump wrote on his Truth Social platform.
Trump met with his National Security Council to discuss the conflict. There was no immediate public statement after the hour and 20 minute meeting.
US officials stressed Trump has not yet made a decision about any intervention.
Hours later, Khamenei responded with a post on X, saying: "We must give a strong response to the terrorist Zionist regime. We will show the Zionists no mercy."
- Evacuations -
Israel's attacks have hit nuclear and military facilities around Iran, as well as residential areas.
Residential areas in Israel have also been hit, and foreign governments have scrambled to evacuate their citizens from both countries.
Since Friday, at least 24 people have been killed in Israel and hundreds wounded, according to Netanyahu's office.
Iran said on Sunday that Israeli strikes had killed at least 224 people, including military commanders, nuclear scientists and civilians. It has not issued an updated toll since then.
More than 700 foreigners living in Iran have crossed into neighbouring Azerbaijan and Armenia since Israel launched its campaign, according to government figures.
On Tuesday in Tehran, long queues stretched outside bakeries and petrol stations as people rushed to stock up on fuel and basic supplies.
Iran's ISNA and Tasnim news agencies on Wednesday reported that five suspected agents of Israel's Mossad intelligence agency had been detained, on charges of tarnishing the country's image online.
With air raid sirens regularly blaring in Tel Aviv, some people relocated to an underground parking lot below a shopping mall.
"We've decided to permanently set camp here until it's all clear, I guess," Mali Papirany, 30, told AFP.
- Nuclear facilities -
After a prolonged shadow war, Israel said its surprise air campaign was aimed at preventing Iran from acquiring nuclear weapons -- an ambition Tehran denies.
The UN nuclear watchdog said there appeared to have been "direct impacts on the underground enrichment halls" at Iran's Natanz facility.
Israel has maintained ambiguity regarding its own atomic activities, but the Stockholm International Peace Research Institute (SIPRI) says it has 90 nuclear warheads.
The conflict derailed a running series of nuclear talks between Tehran and Washington, with Iran saying after the start of Israel's campaign that it would not negotiate with the United States while under attack.
French President Emmanuel Macron said Trump had a critical role to play in restarting diplomacy with Iran, where any attempts at "regime change" would bring "chaos".
