The United Nations chief is calling for a ceasefire in Gaza before “a gigantic tragedy” develops in Rafah if Israel attacks, Al Jazeera reported on Friday.

More than half of Gaza’s 2.3 million population were pushed into Rafah looking for safety from Israel’s military offensive.

“They are living in overcrowded makeshift shelters in unsanitary conditions without running water, electricity and adequate food supplies,” Secretary-General Antonio Guterres said.

Asked if there was a contingency plan for civilians in Rafah to go somewhere else and whether he would push for opening the border to Egypt, Guterres replied: “I think that we should push to avoid the tragedy instead of pushing for things to facilitate the tragedy.”

Egypt has pushed back hard against calls that it take in a mass exodus of Palestinians. It fears Israel won’t allow them to return to Gaza and says it doesn’t want to abet ethnic cleansing.