Iran warned on Saturday it would defend itself after Israeli airstrikes killed at least two soldiers and further stoked fears of a full-scale regional war in the Middle East.
Israel warned Iran would "pay a heavy price" if it responded to the strikes, and the United States, Germany and Britain demanded Tehran not escalate the conflict further.
Other countries, including many of Iran's neighbours, condemned Israel's strikes and some, such as Russia, urged both sides to show restraint and avoid what Moscow dubbed a "catastrophic scenario."
The Islamic republic insisted it had the "right and the duty" to defend itself, while its ally Hezbollah said it had already launched rocket salvos targeting five residential areas in northern Israel.
The Israeli army said 80 projectiles were fired across the border on Saturday.
Confirming its own strikes after explosions and anti-aircraft fire echoed around Tehran, the Israeli military said it had hit Iranian missile factories and military facilities in several regions.