Russia, Germany, UK urge restraint

Russia, Germany and Britain urged countries in the Middle East to show restraint and Israel said it was preparing to "meet all its security needs" in a region on edge over an Iranian threat to strike Israel.

The German airline Lufthansa, one of only two Western carriers flying to Tehran, extended a suspension of its flights to the Iranian capital and Russia warned against travel to the Middle East.

Lufthansa said it would probably not fly to Tehran before April 13. Austrian Airlines said it was still planning to fly but was adjusting timings to avoid crew having to disembark for an overnight layover.

Iran has vowed revenge for the April 1 airstrike on its embassy compound in Damascus that killed a top Iranian general and six other Iranian military officers, ratcheting up tension in a region already strained by the Gaza war.

Israel has not claimed responsibility for the attack, but Iranian Supreme Leader Ayatollah Ali Khamenei said Israel "must be punished and it shall be", saying it was tantamount to an attack on Iranian soil.

Prime Minister Benjamin Netanyahu said Israel was keeping up its war in Gaza but making security preparations elsewhere.

"Whoever harms us, we will harm them. We are prepared to meet all of the security needs of the State of Israel, both defensively and offensively," he said in comments released following a visit to an air force base.

Iran has signaled to Washington that it will respond to Israel's attack in a way that aims to avoid major escalation and it will not act hastily, Iranian sources said.

Conflict has spread across the Middle East since the eruption of the Gaza war, with Iran-backed groups declaring support for the Palestinians waging attacks from Lebanon, Yemen and Iraq. Tehran has avoided direct confrontation with Israel or the United States, while declaring support for its allies.