JERUSALEM—A Syrian missile exploded in southern Israel on Thursday, the Israeli military said, in an incident that triggered warning sirens near the secretive Dimona nuclear reactor and an Israeli strike in Syria. An Israeli military spokesman identified the projectile as an SA-5 surface-to-air missile fired by Syrian forces against Israeli aircraft. He said it overflew its target to reach the Dimona area, 200 km (125 miles) south of the Syrian border. The missile did not hit the reactor, exploding some 30 km (19 miles) away, the spokesman added. The sirens that sounded overnight in the Dimona area followed weeks of heightened tension between Israel and Iran, a close ally of Syrian President Bashar al-Assad, amid renewed global negotiations over Tehran’s nuclear program. For weeks, Israeli media have said air defenses around the Dimona reactor and the Red Sea port of Eilat were being strengthened in anticipation of a possible long-range …