Iran and Israel traded missiles and airstrikes on Saturday, the day after Israel launched a sweeping air offensive against its old enemy, killing commanders and scientists and bombing nuclear sites in a stated bid to stop it from building an atomic weapon.

In Tehran, Iranian state TV reported that around 60 people, including 20 children, had been killed in an attack on a housing complex, with more strikes reported across the country as Israel said it had attacked more than 150 targets.

In Israel, air raid sirens sent residents into shelters as waves of missiles streaked across the sky and interceptors rose to meet them, killing at least three people. An Israeli official said Iran had fired around 200 ballistic missiles in four waves.

U.S. President Donald Trump has lauded Israel's strikes and warned of much worse to come unless Iran quickly accepts the sharp downgrading of its nuclear programme that the U.S. has demanded in talks that had been due to resume on Sunday.

But with Israel saying its operation could last weeks, and urging Iran's people to rise up against their Islamic clerical rulers, fears have grown of a regional conflagration dragging in outside powers, with global economic and financial repercussions.

The United States, Israel's main ally, helped shoot down Iranian missiles, two U.S. officials said.

Iranian fire still struck residential districts in Israel, however, and Defence Minister Israel Katz said Iran's leadership had crossed a red line.

"If (Supreme Leader Ayatollah Ali) Khamenei continues to fire missiles at the Israeli home front, Tehran will burn," he said in a statement.

Iran had vowed to avenge Friday's Israeli onslaught, which gutted Iran's nuclear and military leadership and damaged atomic plants and military bases, killing 78 people, including civilians, according to Iran's U.N. envoy.

Tehran warned Israel's allies that their regional military bases would come under fire too if they help shoot down Iranian missiles, Iranian state television reported.

Iran's own ally, the Yemeni Houthi group, fired missiles at Israel on Friday night, but at least one appeared to go astray, injuring five Palestinians, including three children, in the Israeli-occupied West Bank, the Palestinian Red Crescent said.

However, 20 months of war in Gaza and a conflict in Lebanon last year have decimated Tehran's strongest allies, Hamas in Gaza and Hezbollah in Lebanon, reducing its ability to project power across the region, along with its options for retaliation.

Gulf Arab states that have long mistrusted Iran but fear coming under attack in any wider conflict have urged calm as worries about disruption to the Gulf region's crucial oil exports boosted the price of crude by about 7% on Friday.

NIGHT OF BLASTS AND FEAR IN ISRAEL AND IRAN

Iran's overnight fusillade included hundreds of ballistic missiles and drones, an Israeli official said. Three people, including a man and a woman, were killed and dozens wounded, the ambulance service said.

In Rishon LeZion, south of Tel Aviv, emergency services rescued a baby girl trapped in a house hit by a missile, police said. The video showed teams searching through the rubble of one home.

And in the western suburb of Ramat Gan, near Ben Gurion airport, Linda Grinfeld described her apartment being damaged: "We were sitting in the shelter, and then we heard such a boom. It was awful."

The Israeli military said it had intercepted surface-to-surface Iranian missiles as well as drones, and that two rockets had been fired from Gaza.

With Iran's air defences heavily damaged, Israeli Air Force chief Tomer Bar said "the road to Iran has been paved".