Israel complained to the UN peacekeeping force after three Syrian tanks entered the demilitarized zone in the Golan Heights, a military official told the AP on conditions of anonymity. The tanks crossed the border Saturday. According to the Israeli news site Ynet, the tanks and two armored personnel carriers drove a few kilometers from Israeli military positions. Israel is concerned that the ongoing civil conflict in Syria could spill over their border. Golan Heights are a plateau bordering south Syria seized by Tel Aviv from Damascus in the 1967 War. The UN has been deploying peacekeeping forces to the zone since 1974 to maintain the ceasefire. Despite the unsettled international status of Golan Heights, Israel has been constructing own settlements there since the 1970s.