JERUSALEM—The Israeli military said Thursday that a Syrian missile that reached deep into Israeli territory and set off air raid sirens near the country’s top-secret nuclear reactor was the result of a misfire and not a deliberate attack. The missile landed in southern Israel early Thursday, prompting Israel to respond with airstrikes on the missile launcher and other targets in Syria. The army’s chief spokesman, Brig. Gen. Hidai Zilberman, was quoted as telling military correspondents that the Israeli air force was already operating in Syrian airspace when the anti-aircraft missile was fired. He said the projectile, identified as a Russian-made SA-5 missile, missed its target and exploded in southern Israel. The missile, also known as an S200, set off air raid sirens in a village near Dimona, the southern desert town where Israel’s nuclear reactor is located, and some 200 miles south of Damascus. “There was no intention of hitting …