Israeli forces struck the southern Gaza town of Rafah twice overnight, sowing fear in one of the last places where civilians can seek refuge. Israel has widened its offensive against Hamas from the devastated north to southern areas already packed with displaced people. United Nations officials say there are no safe places in Gaza. Heavy fighting in and around the southern city of Khan Younis has displaced tens of thousands of people and cut most of Gaza off from deliveries of food, water and other vital aid. U.N. Secretary-General Antonio Guterres used a rarely exercised power to warn the Security Council of an impending “humanitarian catastrophe” and urged members to demand a cease-fire. The United States appeared likely to block any such effort.