JERUSALEM (AP) — The Israeli military said Tuesday that Iran has fired missiles and it ordered residents to remain close to bomb shelters 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.

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.

Iranian media began posting videos that appeared to show missile launches at several sites across the country. However, the Iranian government did not immediately acknowledge what was happening.

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.