GAZA CITY, Gaza Strip (AP) — Palestinian families fled neighborhoods on the outskirts of Gaza City as Israel unleashed heavy artillery fire and airstrikes. Israel said it was clearing a network of militant tunnels. Israel has massed troops along the border and called up 9,000 reservists as fighting intensifies with the Islamic militant group Hamas, which controls the Gaza Strip. Palestinian militants have fired some 1,800 rockets, and the Israeli military has launched more than 600 airstrikes and shelled some areas with tanks. As Israel and Hamas plunged closer to all-out war, communal violence in Israel erupted again overnight. Separately, in the West Bank, Palestinian health officials say seven Palestinians were killed in several locations by Israeli army fire.