Iran said it fired dozens of missiles into Israel on Tuesday, a sharp escalation of the monthslong conflict between Israel and the Iran-backed militias Hezbollah and Hamas. There were no immediate reports of casualties as Israel ordered residents to head to bomb shelters and as air raid sirens sounded across the country.

A series of window-shaking explosions were heard in Tel Aviv and near Jerusalem, though it was not immediately clear whether the sounds were from missiles landing or being intercepted by Israeli defenses, or both.

Israel and the United States have warned there would be severe consequences in the event of an attack on Israel from Iran, which backs the militant group Hezbollah in Lebanon. President Joe Biden and Vice President Kamala Harris monitored the attack on Israel from the White House Situation Room.

Israeli army spokesman Rear Adm. Daniel Hagari said the country's air defense system was fully operational, detecting and intercepting threats. “However, the defense is not hermetic,” he said.

Orders to shelter in place were sent to Israelis’ mobile phones and announced on national television.

Iran took responsibility for launching dozens of ballistic missiles at Israel. The claim was made in a statement read aloud on state television.

In its statement, Iran referenced Hezbollah leader Hassan Nasrallah and Revolutionary Guard Gen. Abbas Nilforushan, both killed in an Israeli airstrike last week in Beirut. It also mentioned Ismail Haniyeh, a top leader in Hamas who was assassinated in Tehran in a suspected Israeli attack in July. It warned this attack represented only a “first wave,” without elaborating.

The air raid alerts in Israel came a day after Israel said it had begun limited ground operations against Hezbollah in southern Lebanon.

Israeli airstrikes and artillery fire pounded southern Lebanese villages where people were ordered to evacuate, and Hezbollah militants responded by firing a barrage of rockets into Israel. There was no immediate word on casualties as fighting intensified and concerns of a wider regional war grew.

A senior White House official warned of “severe consequences” should Iran launch a ballistic missile against Israel. U.S. ships and aircraft are positioned in the region to assist Israel in the event of an attack from Iran. The official spoke on condition of anonymity to discuss intelligence.

Hagari also warned of consequences if Iran fired missiles into Israel.

He urged the public to stay close to sheltered areas. “The Iranian strike could be widespread,” he said.

Iranian officials could not be immediately reached for comment.

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

While Hezbollah denied Israeli troops had entered Lebanon, the Israeli army announced it had also carried out dozens of ground raids into southern Lebanon going back nearly a year. Israel released video footage purporting to show its soldiers operating in homes and tunnels where Hezbollah kept weapons.

If true, it would be another humiliating blow for Iran-backed Hezbollah, the most powerful armed group in the Middle East. Hezbollah has been reeling from weeks of targeted strikes that killed its leader, Hassan Nasrallah, and several of his top commanders.

On Tuesday morning, Israel warned people to evacuate to the north of the Awali River, some 60 kilometers (36 miles) from the border and much farther than the Litani River, which marks the northern edge of a U.N.-declared zone intended to serve as a buffer between Israel and Hezbollah after their 2006 war.

The border region has largely emptied out over the past year as the two sides have traded fire. But the scope of the evacuation warning raised questions as to how deep Israel plans to send its forces into Lebanon.

An Israeli airstrike hit a residential building near Beirut Tuesday, causing damage but with no immediate reports of casualties. The strike appeared to hit an apartment about 100 meters from the Iranian Embassy.

Anticipating more rocket attacks from Hezbollah, the Israeli army announced new restrictions on public gatherings and closed beaches in northern and central Israel. The military also said it was calling up thousands more reserve soldiers to serve on the northern border.