Israel launched strikes across Iran on Friday, saying they targeted the “heart” of Iran’s nuclear programme.
With counter-attacks expected “in the immediate future”, a state of emergency was declared in Israel.
Hossein Salami, chief of Iran’s Islamic Revolutionary Guards – a powerful branch of the country’s armed forces – was killed, Iranian state media reported, as well as nuclear scientists.
The US said it was not involved in the strikes, which also hit Iran’s main nuclear enrichment facility.
Explosions were reported in Iran’s capital Tehran around 03:30 local time (0100 BST).
Iranian state media said residential areas were hit, with blasts also heard north-east of Tehran. The BBC is not able to independently verify these reports.
In Israel, residents were woken by air raid sirens around the same time and received emergency phone alerts.
Hours after the initial strikes, an explosion was reported at the Natanz nuclear facility, which is located about 225km (140 miles) south of the capital, according to Iranian state media.
Reuters An apartment block partially destroyed by explosions Reuters
Iranian state media reported residential areas in Tehran were hit after Israel launched strikes across the country
Israeli Prime Minister Benjamin Netanyahu said the strikes – called Operation Rising Lion – were “a targeted military operation to roll back the Iranian threat to Israel’s very survival”.
He said the operation would “continue for as many days as it takes to remove the spread”.
“In recent months, Iran has taken steps that it has never taken before, steps to weaponise this enriched uranium.
“If not stopped, Iran could produce a nuclear weapon in a very short time. It could be a year. It could be within a few months, less than a year. This is a clear and present danger to Israel’s very survival.”
In his address, Netanyahu also thanked US President Donald Trump for “confronting Israel’s nuclear weapons programme”.
An Israeli military official told the BBC that Iran had enough nuclear material to create nuclear bombs “within days”.
A spokesperson for Iran’s armed forces has said that the US and Israel will pay a “heavy price” for the strikes, according to Reuters.
“The armed forces will certainly respond to this Zionist attack,” said Iranian spokesperson, Abolfazl Shekarchi.
US Secretary of State Marco Rubio said it was not involved with the strikes and did not provide any assistance.
He said the top priority for the US was to protect American forces in the region.
Trump has yet to comment on the strikes.
In other international reaction, Australia’s Foreign Minister Penny Wong said they were “alarmed by the escalation” and that the strikes risked “further destabilising a region that is already volatile”.
What is Iran’s nuclear programme?
A map showing Iran’s nuclear sites
Iran has long maintained that its nuclear programme is for civilian purposes only. It has several facilities around Iran, at least some of which have been targeted in the Israeli strikes.
But many countries – as well as the global nuclear watchdog, the International Atomic Energy Agency (IAEA) – are not convinced Iran’s programme is for civilian purposes alone.
This week, the watchdog’s board of governors formally declared Iran in breach of its non-proliferation obligations for the first time in 20 years.
It cited Iran’s “many failures” to provide full answers about undeclared nuclear material and Iran’s stockpile of enriched uranium.
An earlier IAEA report said Iran had enriched uranium to 60% purity, enough near weapons grade uranium to make nine nuclear bombs.
