GENEVA The United Nations humanitarian office said on Tuesday that nearly 200,000 people or nearly a tenth of the population, have fled their homes in Gaza since the start of hostilities and is poised for shortages of water and electricity due to a blockade.

"Displacement has escalated dramatically across the Gaza strip, reaching more than 187,500 people since Saturday. Most are taking shelter in schools," Jens Laerke, OCHA spokesperson, told a Geneva briefing, saying further displacement was expected as clashes continue.

A World Health Organization spokesperson said it had reported 13 attacks on health facilities in the Gaza strip since the weekend and said that its medical supplies stored there had already been used up.

(Reporting by Emma Farge, Editing by Rachel More)