UN Secretary-General Ban Ki-moon Thursday condemned a deadly attack on a U.N. school for Palestinian refugees in northern Gaza that killed a number of civilians who sought refuge there from Israeli shelling as well as U.N. staff. In a statement, Ban again demanded that Israel and Hamas abide by international humanitarian law during their conflict and respect "the sanctity of civilian life, the inviolability of U.N. premises," and protect humanitarian workers. The U.N. chief said that the "circumstances (of the attack) are still unclear." Ban said that U.N. staff are attempting to arrange "a humanitarian pause in the hostilities so that civilians could be evacuated." "Today's attack underscores the imperative for the killing to stop – and to stop now," Ban said.