UPDATE : What prompted Israel to attack Iran - and why now

 UPDATE : What prompted Israel to attack Iran - and why now

Speculation about an Israeli attack on Iran's nuclear sites has swirled around for years, but it intensified significantly in the past few days. On Thursday, US media reported such an attack was imminent.

Israel has been worried that talks between the US and Iran (which have been going on since April) on a new nuclear deal might leave Iran with a nuclear programme - something Israel has said it cannot accept in any form.

It has warned for years of what it perceives to be an existential threat from Iran's nuclear programme. Israel's PM Benjamin Netanyahu has made it a constant theme, from as far back as the mid-1990s.

Iran has continuously denied seeking nuclear weapons, insisting its nuclear programme is for peaceful, civilian purposes only.

But Western powers, and the global nuclear body the International Atomic Energy Agency (IAEA), are not satisfied this is the case. On Thursday, the IAEA passed a resolution - for the first time in 20 years - declaring Iran in breach of its nuclear obligations.

Speaking as the attacks got under way, Netanyahu said Iran had produced enough material for - theoretically - nine nuclear bombs, something in line with a recent IAEA assessment. Iran, he said, threatened Israel's "very survival".

It seems in deciding to attack now, Israel is taking advantage of a window: Iran has not yet rebuilt air defences which were degraded by an Israeli attack in October - and a strike pre-empts the next round of nuclear talks which are due to take place on Sunday.

Iran's Supreme Leader Ayatollah Ali Khamenei says Israel "should anticipate a severe punishment" following overnight strikes which targeted nuclear sites and killed several military commanders.

He says Israel has "committed a crime in our dear country today" and his military forces "won’t let them go unpunished".

"With this crime, the Zionist regime has prepared for itself a bitter, painful fate, which it will definitely see."

Iran has since launched about 100 drones towards Israel, according to the Israel Defense Forces (IDF).