Israel pounded Lebanon early Thursday and said it intercepted missiles from Iran as a widening war launched by the United States and Israel also brought fresh turmoil to Iraq.

An air strike in the pre-dawn hours struck a Beirut suburbs stronghold of Hezbollah, the Tehran-backed force that has vowed to avenge the death of Iran's supreme leader, Ayatollah Ali Khamenei, in the war's first moments Saturday.

Israel, which had warned residents beforehand to flee, also said it was working to intercept a new barrage of missiles fired by Iran, even though the US military had boasted of crippling the Islamic republic's capacities.

Iran has vowed to exert a heavy price for the attacks and has fired missiles across the region, and its elite Revolutionary Guards claimed Wednesday to have closed the Strait of Hormuz, the chokepoint into the Gulf through which a fifth of the world's crude oil flows.

"The Americans' mischief and deceit could lead to the collapse of the entire military and economic infrastructure of the region," the Iranian military command warned in a statement.

Oil tanker transits through the strait have plunged by 90 percent, energy market intelligence firm Kpler said.