That was U.S. President Joe Biden's answer Friday when asked what his message to Iran was as Israel prepares for a possible attack.

"We will support Israel. We will help defend Israel and Iran will not succeed."

Warnings grew of retaliation for the killing last week of a senior Iranian commander in the country's embassy in Damascus.

Israel did not claim responsibility for the airstrike.

But Iran's supreme leader, Ayatollah Ali Khamenei, said Israel "must be punished and shall be" for an operation he said was equivalent to an attack on Iranian soil.

Countries including India, France, Poland and Russia have warned their citizens against travel to the region, already on edge over the war in Gaza, now in its seventh month.

Germany and Austria on Friday called on their citizens to leave Iran.

The Israeli military said it had not issued fresh instructions to civilians, but Spokesperson Rear Admiral Daniel Hagari asked people to remain vigilant.

"We are prepared and are on high alert, both defensively and offensively, and we will know how to both inform the public and deal with any threat."

Meanwhile, on Friday, dozens of missiles were intercepted in the sky over the Israel-Lebanon border.

The Israeli army said others had fallen in open areas and no injuries were reported.