UN Secretary-General Antonio Guterres condemned the death of at least 18 people, including children, women and six United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) staff, in Israeli airstrikes that hit a school serving as a shelter in Nuseirat yesterday. "This incident raises the number of UNRWA staff killed in this conflict to 220," the Secretary-General urged in a statement released by his spokesperson Stephane Dujarric on Thursday. "-- This incident must be independently and thoroughly investigated to ensure accountability. "The continued lack of effective protection for civilians in Gaza is unconscionable. "Civilians and the infrastructure they rely on must be protected and the essential needs of civilians met," according to the statement. The Secretary-General calls upon all parties to refrain from using schools, shelters, or the areas around them for military purposes. "All parties to the conflict have the obligation to comply with international humanitarian l aw at all times. "The Secretary-General reiterates his call for an immediate ceasefire and the immediate and unconditional release of all hostages. This horrific violence must stop, the statement added. Source: Kuwait News Agency