"We have embarked on the most complex campaign in our history to remove a threat of such magnitude, against such an enemy. We must be ready for a prolonged campaign," Zamir said in a video statement to Israelis.

Israel launched attacks against Iran last Friday which have combined targeted assassinations of key military personnel with strikes on Iran's nuclear and missile facilities.

Zamir said the Israeli military had prepared for "years" for the campaign against Iran, even while Israeli troops continue their devastating campaign against the Palestinian militant group Hamas in Gaza.

The Iranian "operation was made possible thanks to the convergence of operational and strategic conditions, some of which were temporary," Zamir said, adding that "history would not forgive us if we failed to act now" against an "existential threat" to Israel.

Analysts say Iran was severely weakened by Israeli strikes on allied militant groups Hamas in Gaza and Hezbollah in Lebanon since 2023, while Israel damaged Tehran's air defences in tit-for-tat exchanges between the countries last year.

Zamir hailed "extraordinary results" from fighter jet pilots flying missions "at the greatest range and intensity in the (air) force's history".

He also said that Israelis needed to brace for more difficulties, as the country comes under daily attack from Iranian ballistic missiles.

"Although we have made significant achievements, difficult days still lie ahead. We must remain alert and united until the mission is complete," he added.