Iran is planning to ‘give a harsh response’ to an Israeli attack launched early on Friday against its nuclear programme, an Iranian security source told Reuters.

“The response to the Israeli attack will be harsh and decisive,” the official said, adding that details of Iran’s “retaliation are being discussed at the highest levels” when asked whether the attack would be imminent.

This after Israel said it targeted Iran’s nuclear facilities, ballistic missile factories and military commanders at the start of what it warned would be a prolonged operation to prevent Tehran from building an atomic weapon.

Iranian media and witnesses reported explosions, including at the country’s main uranium enrichment facility at Natanz, while Israel declared a state of emergency in anticipation of retaliatory missile and drone strikes.

Iranian state television reported that Hossein Salami, the chief of the elite Revolutionary Guards corps, had been killed and the unit’s headquarters in Tehran had been hit. Several children had been killed in a strike on a residential area in the capital, it said.

“We are at a decisive moment in Israel’s history,” Israeli Prime Minister Benjamin Netanyahu said in a recorded video message.

“Moments ago, Israel launched Operation Rising Lion, a targeted military operation to roll back the Iranian threat to Israel’s very survival. This operation will continue for as many days as it takes to remove this threat.”

Iran’s Supreme Leader, Ayatollah Ali Khamenei, said in a statement that Israel had “unleashed its wicked and bloody” hand in a crime against Iran and that it would receive “a bitter fate for itself”.