Iran fired a salvo of ballistic missiles at Israel on Tuesday in retaliation for Israel's campaign against Tehran's Hezbollah allies in Lebanon.

Alarms sounded across Israel and explosions could be heard in Jerusalem and the Jordan River valley after Israelis piled into bomb shelters. Reporters on state television lay flat on the ground during live broadcasts.

Iran's Revolutionary Guards said Iran had launched tens of missiles at Israel, and that if Israel retaliated Tehran's response would be "more crushing and ruinous".

A senior Iranian official later said that the order to launch missiles at Israel was made by the country's Supreme Leader Ayatollah Ali Khamenei. Khamenei remains in a secure location, the senior official added.

The Israeli army said Israel's airspace was closed following the Iranian attack.

Journalists saw missiles intercepted in the airspace of neighbouring Jordan. Israeli army radio said nearly 200 missiles had been launched into Israel from Iran.

Earlier, the military had announced that any ballistic missile strike from Iran was expected to be widespread and told the public to shelter in safe rooms in the event of an attack.

Iran has vowed to retaliate following attacks that killed the top leadership of its Hezbollah allies in Lebanon.

The firing of missiles came after Israel said its troops had launched ground raids into Lebanon, though it described the forays as limited. The Israeli campaign in Lebanon is the biggest escalation of regional warfare since fighting erupted in Gaza a year ago.

In Washington, US President Joe Biden said the United States was prepared to help Israel defend itself from Iranian missile attacks.

The Iranian missile launches came after Israeli ground troops launched raids into Lebanon and its warplanes bombed from the skies. (Reuters)