Gaza conflict: UN says number of displaced almost doubles
The number of people in Gaza seeking sanctuary from the conflict with Israel nearly doubled on Friday, the UN says.
Relief workers in Gaza said there were now more than 40,000 people being protected in 34 UN shelters.
It comes after Israel sent troops and tanks into Gaza on Thursday, targeting Hamas militants who are firing rockets into Israel.
UN Secretary-General Ban Ki-moon is due to the region on Saturday to meet both sides.
The UN Security Council is holding an emergency session to discuss the conflict in Israel and Gaza.
Earlier on Friday, Israeli Prime Minister Benjamin Netanyahu has warned of a "significant expansion" of the offensive.
Hamas, the Palestinian group that controls Gaza, said Israel would "pay a high price" for the invasion.
Mr Ban's visit would aim to help Israelis and Palestinians "end the violence and find a way forward", UN political affairs chief Jeffrey Feltman said.
"Israel has legitimate security concerns, and we condemn the indiscriminate rocket fire from Gaza into Israel. But we are alarmed by Israel's heavy response," he added.
The Palestinian ambassador to the UN, Riyad Mansour, said Israel's "savage" operation in Gaza was "not self-defence" but "a vengeful military aggression".
Israel's ambassador to the UN Ron Prosor said: "Israel was left with no choice" as Hamas was using ambulances filled with children "to move their terrorists around Gaza".
Thousands of Palestinians had already fled their homes in Gaza after 10 days of cross-border rocket fire and Israeli air strikes.
But the numbers spiked after thousands of Israeli troops backed with tanks, helicopters and artillery fire poured across the border late on Thursday.
"The ground invasion is a bad move because it is going to kill more innocent civilians and would do no good for Israelis." - Abdelraziq, business and management graduate, Gaza
"The ground invasion is a necessary evil. The last thing that Israel would like to do is to risk the lives of its own soldiers and the lives of innocent people, but we have to stop the firing of the rockets and destroy the tunnels." - Doron Youngerwood, marketing manager, Modiin, Israel
The number of people seeking sanctuary in UN shelters in Gaza rose from 22,000 to over 40,000 on Friday, said Christopher Gunness, a spokesman for the United Nations Relief and Works Agency (UNRWA).
"We have also launched a $60m (£35m) appeal for our emergency work," he added.
The BBC's Yolande Knell in Gaza City says Israeli aircraft and artillery intensified strikes in the north, east and south of Gaza on Friday.
Meanwhile, air raid sirens sounded in towns across southern Israel as rocket attacks from Gaza continued.
At least 48 Palestinians have been killed since the ground offensive began, officials in Gaza said. One Israeli soldier also died.
The dead included three Palestinian children killed by Israeli tank fire in the north of Gaza, medics added.
At least 290 Palestinians - three-quarters of them civilians - have died since the start of the wider Israeli operation on 8 July, officials in Gaza say.
One Israeli civilian has been killed by mortar fire and several Israelis have been seriously injured.
Mr Netanyahu said the ground operation was targeting the Hamas tunnel network, which the Israel military could not do "only from the air".
Mr Netanyahu said he ordered troops in after attempts to get Hamas to agree to a ceasefire failed.
Palestinian militants have used tunnels to carry out attacks, some of which have been thwarted by the Israeli military.
Hamas spokesman Sami Abu Zuhri reacted defiantly to the Israeli offensive, declaring: "Netanyahu is killing our children and will pay the price."
Israel says it has carried out more than 1,960 attacks on Gaza since 8 July, while militants have fired some 1,380 rockets at Israel. It says more than 50 rockets have been fired at Israel since the ground operation began.
The UN says at least 1,370 homes have been destroyed in Gaza and more than 18,000 people displaced in recent hostilities.