The United Nations on Monday said 123,538 people in Gaza have been internally displaced, mostly "due to fear, protection concerns and the destruction of their homes".
The Office for the Coordination of Humanitarian Affairs (OCHA) added that 73,000 people are sheltering in schools, reports BBC.
Adnan Abu Hasna - spokesperson for the UN agency for Palestinian refugees (UNRWA) - expects numbers to rise.
"There's electricity in these schools, we provide them with a meal, clean water, psychological support and medical treatment," he says.
There are 2.3 million Palestinians living in Gaza. Before launching its retaliatory air strikes on Saturday, Israel warned people living in certain areas to leave.
"I'm telling the people of Gaza: get out of there now, because we're about to act everywhere with all our force," Israeli Prime Minister Benjamin Netanyahu said on Saturday.