Explosions were heard over Tel Aviv and Jerusalem as sirens sounded on Friday night across Israel following what the country's military spokesman said was the firing of missiles from Iran.

Iran's state news agency IRNA said hundreds of ballistic missiles had been launched in retaliation for Israel's biggest ever attacks on Iran, blasting Iran's huge underground nuclear site at Natanz and wiping out its top military commanders.

There were no immediate reports of deaths or injuries.

Israel said the strikes were the start of "Operation Rising Lion". Iran's Supreme Leader Ayatollah Ali Khamenei accused Israel of having started the strikes and initiating a war.

U.S. President Donald Trump said it was not too late for Tehran to halt the bombing campaign by reaching a deal on its nuclear programme.

As evening fell on Friday, Iranian media reported explosions on the northern and southern outskirts of Tehran and at Fordow, near the holy city of Qom, a second nuclear site which had been spared in the first wave of attacks.