Israel has issued an "urgent warning to Iranian citizens" to evacuate areas close to military sites after fresh exchanges of strikes between the two countries overnight raised fears of further escalation.

Prime Minister Benjamin Netanyahu of Israel presented Iran’s sophisticated ballistic missiles as a critical threat to Israel’s survival.

The region braced for a protracted conflict after Israel’s surprise bombardment of Iran’s nuclear and military sites on Friday killed several top generals and nuclear scientists, and neither side showed any sign of backing down.

Smoke and flames filled the sky over Tehran as Israel struck oil and gas facilities in the Iranian capital and targeted more nuclear facilities during attacks that carried on into Sunday after starting two days earlier.

Maj. Gen. Yadlin, who flew in the 1981 Osirak reactor strike, explains why Israel's current operation against Iran represents a complex, multi-week campaign.

Israel and Iran bombarded each other for a third day, with international concern growing that the conflict will spread across one of the world’s key oil-producing regions.