GAZA CITY, Gaza Strip (AP) - Israeli airstrikes on Gaza City flattened three buildings and killed at least 42 people Sunday, medics said, making it the deadliest single attack since heavy fighting broke out between Israel and the territory's militant Hamas rulers nearly a week ago.The violence, which came as international mediators worked to broker a cease-fire and stave off an Israeli ground invasion of the territory, marked the worst fighting here since the devastating 2014 war in Gaza.The airstrikes Sunday hit a busy downtown street of residential buildings and storefronts over the course of five minutes just after midnight, destroying two adjacent buildings and one about 50 yards (meters) down the road.RELATED: Israeli airstrike.