Israel targeted Iran's air defences and missile launchers on Saturday as it pressed its bid to dismantle its arch-foe's military capabilities, after a night of mutual attacks.

Israel's massive strikes on Iran, which it calls an existential threat, have hit nuclear and military facilities, killed top commanders and dozens of civilians, and sought to destroy the country's defence capabilities.

Iran has hit back with volleys of missiles that lit up the night sky over Jerusalem and Tel Aviv, killing three people and wounding dozens.

Following decades of enmity and conflict by proxy, it is the first time that Israel and Iran have traded fire with such intensity, with fears of a prolonged conflict engulfing the region.

Israel began striking Iran early on Friday in an operation it has dubbed "Rising Lion", and has since killed several top Iranian generals, including senior leaders of the Revolutionary Guards' air arm.

On Saturday, Israel's military said it was striking dozens of missile launchers in Iran after announcing it had targeted air defences with a wave of strikes in the Tehran area.

Two senior Iranian generals have been killed in Israeli strikes, Iranian state television reported on Saturday, as Israel kept up its assault.

Iran's ambassador to the United Nations said on Friday that 78 people had been killed and 320 wounded in the first wave of strikes by Israel.

Iran called on its citizens to unite in defence of the country as Israeli Prime Minister Benjamin Netanyahu urged them to rise up against their government.

Air raid sirens and explosions rang out across Israel through the night, with many residents holed up in bomb shelters until home defence commanders stood down alerts. (AFP)