In a press statement sent to Xinhua, the United Nations Relief and Works Agency for Palestine Refugees (UNRWA) said "218,600 internally displaced persons now reside in 92 schools affiliated with the UN agency in various areas of the Gaza Strip."

The UNRWA said many others are sheltering in government schools and other buildings, noting that the number of the displaced is increasing on a daily basis.

The UN agency added that the shelters are overcrowded, with a limited amount of food, non-food items, and potable water.

"The water crisis is looming in UNRWA shelters and throughout Gaza due to the lack of electricity needed to operate pumps and water desalination plants and the limited water supply in the local market," the UNRWA warned.

Hamas launched on Saturday a surprise attack on southern Israeli towns adjacent to Gaza, prompting Israel to launch retaliatory strikes on the Palestinian enclave. The exchanges of fire have left a heavy toll on both sides.