U.S. urges Americans in Israel to head to BOMB SHELTERS ahead of 'imminent' ballistic missile attack from Iran

The U.S. Embassy in Israel told its employees to return home and be prepared to enter bomb shelters as the White House warned of an imminent attack from Iran.

The warning comes a day after Israeli forces launched a ground invasion of southern Lebanon on Monday night aimed at crippling the Iranian-backed militia Hezbollah there.

Now, Iran is preparing to 'imminently' launch a ballistic missile attack on Israel, the White House warned, adding such action would carry 'severe consequences.'

'The United States has indications that Iran is preparing to imminently launch a ballistic missile attack against Israel,' a senior administration official told DailyMail.com.

'We are actively supporting defensive preparations to defend Israel against this attack. A direct military attack from Iran against Israel will carry severe consequences for Iran.'

The order from U.S. Embassy, the first such order in months, indicates the severity of the situation. 

Three Israeli officials told The New York Times the attack would involve unmanned drones and missiles fired toward Israel.

The attack raises the possibility of all-out war between the two bitter enemies, who have fought a shadow war for years as Tehran sought to destroy Israel and Israel tried to rein in Iran's nuclear program. 

Iran launched a direct attack on Israel in April, but few of the missiles reached their targets. Many were shot down by a U.S.-led coalition, while others apparently failed at launch or crashed in flight.

But a western source told Axios that unlike the April attack, this time Iran is expected to attack Israel only with ballistic missiles that reach Israel within 12 minutes and not with drones or cruise missiles that allow for much longer preparation time for defense and interception.

Israeli attacks on Lebanon have been escalating as they move to pick off the top leaders of Hezbollah. 

Over the past year, Hezbollah has been attacking Israel in solidarity with Hamas, the Gaza-based armed group also backed by Iran.

The Pentagon said on Monday that the U.S. was sending a few thousand additional forces to the Middle East to bolster the 40,000 already in the region and to help defend Israel.

Israeli Prime Minister Benjamin Netanyahu said in a Tuesday statement that Israel is facing 'large challenges' as it fights an Iranian axis. 

In the videotaped statement, he urges the public to listen to public safety guidelines from the army´s Home Front Command. He made no direct mention of a missile threat. 

Israeli Defense Forces spokesman Rear Admiral Daniel Hagari declared that Israeli officials had received the intelligence update from Washington but that no aerial threats from Iran had yet been detected.

He said Israel and its allies are in a 'high state of readiness' and any attack from Iran would have repercussions, while the US Embassy in Jerusalem instructed its employees and families to 'shelter in place'. 

A large-scale attack by Iran on Israel could trigger all-out war in the Middle East, with experts warning any such escalation would likely see the US come to Israel's defence.

Fears of an Iranian attack were raised as the Israeli military warned the residents of more than two dozen Lebanese border communities to immediately evacuate their homes after announcing the start of ground operations against Hezbollah late last night.

IDF spokesman Avichay Adraee told Lebanese citizens to flee north of the Awali River, some 60 kilometres (36 miles) from the border, raising fears that the IDF may intend to send its forces deep into southern Lebanon or step up the intensity of airstrikes.

'You must head north of the Awali River to save yourselves and leave your houses immediately,' said the statement.