Israel-Gaza-Lebanon updates: US helps shoot down missiles in Iranian barrage

The Israel Defense Forces issued a warning for residents of the "Dan area," referring to the greater Tel Aviv area, to stay "near a shelter until further notice."

Sirens sounded in central Israel, the IDF said in a second statement, after issuing the warning to stay in shelters. The sirens sounding in central Israel were due to launches from Lebanon, the IDF told ABC News.

"From this moment, Israelis living in central Israel are advised to stay by their safe rooms. Enter them during sirens and stay there until further notice," IDF spokesperson Daniel Hagari said in Hebrew.

-ABC News' Dana Savir, Anna Burd and Jordana Miller

The U.S. Embassy in Jerusalem issued a statement directing all government employees and their family members "to shelter in place until further notice," following reports of an imminent Iranian missile attack on Israel.

The embassy noted the "continued need for caution and increased personal security awareness as security incidents, including mortar and rocket fire and unmanned aircraft system," which it said "often take place without warning."

"The security environment remains complex and can change quickly depending on the political situation and recent events," it added.

Prime Minister Benjamin Netanyahu urged unity among Israelis in a video statement published Tuesday, as Israel Defense Forces operations in Lebanon expanded and amid fears of an imminent Iranian missile attack.

"We are in the midst of a campaign against Iran's 'Axis of Evil,'" the prime minister said. "These are days of great achievements and great challenges."

The "great achievements," Netanyahu said, included the assassination of Hezbollah leader Hassan Nasrallah in a Beirut airstrike last week, plus the defeat of an alleged Hezbollah plan to launch an infiltration attack into northern Israel.

The country still faces "big challenges," he continued.

"What I ask of you is two things: One -- to strictly obey the directives of the front-line command, it saves lives. And second -- to stand together. We will stand firm together in the testing days ahead."

"Together we will stand, together we will fight and together we will win."

-ABC News Joe Simonetti and Jordana Miller

A senior White House official told ABC News on Tuesday that the U.S. "has indications that Iran is preparing to imminently launch a ballistic missile attack against Israel."

"We are actively supporting defensive preparations to defend Israel against this attack," the official added.

"A direct military attack from Iran against Israel will carry severe consequences for Iran."

Israel Defense Forces spokesperson Rear Adm. Daniel Hagari told reporters, "At this moment we don't identify an aerial threat from Iran."

"The U.S. informed us that Iran is preparing to fire directly on Israel," he said, asking the public to be "responsible and vigilant and I will be here to update you."

A senior Israeli official told ABC News, "If Iran attacks Israel the reaction will be severe."

-ABC News' Selina Wang, Joe Simonetti, Jordana Miller and Eric Avram