Fears heightened that the Middle East is on the brink of war after Iran fired a barrage of ballistic missiles at Israel Tuesday evening, forcing the entire civilian population to be ordered into bomb shelters as sirens sounded across the country.

Iran took responsibility 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 the attack represented only a “first wave,” without elaborating.