More than 123,000 people have been displaced in the Gaza Strip since the outbreak of the conflict between Palestinian fighters and Israeli forces, the United Nations said on Monday.
"As many as 123,538 people, have been internally displaced in Gaza, mostly due to fear, protection concerns and the destruction of their homes," said the UN's humanitarian agency, OCHA.
More than 73,000 are sheltering in schools, OCHA said, some of which have been designated emergency shelters.
Israel has launched hundreds of strikes on Gaza since Saturday, when Hamas militants launched deadly attacks in Israel and fired thousands of rockets at the country.
Adnan Abu Hasna, a spokesman for the UN agency for Palestinian refugees (UNRWA), said he expected the numbers to rise further.
"There's electricity in these schools, we provide them with a meal, clean water, psychological support and medical treatment," he told AFP.
Gaza is home to 2.3 million Palestinians, who have lived under a crippling Israeli blockade imposed after Hamas took power in 2007.
As many as 413 deaths were reported from Gaza Strip as Israeli troops unleashed a reign of terror desperately wanting to regain control of the desert around the Gaza and evacuate people from the embattled border area on Monday, as the death toll from the war with Hamas surged above 1,100 by the third day of clashes.
Prime Minister Benjamin Netanyahu warned Israel on Sunday to prepare for a "long and difficult" conflict a day after Palestinian group Hamas launched a surprise assault from Gaza, firing a barrage of rockets and sending a wave of fighters who gunned down civilians and took at least 100 hostages.
More than 700 Israelis have been killed since Hamas launched its large-scale attack, according to the Israel Defense Forces (IDF) on Monday -- the country's worst losses since the 1973 Arab-Israeli war.
Gaza officials reported at least 413 deaths in the impoverished and blockaded enclave of 2.3 million people, which was hammered by Israeli air strikes on 800 targets ahead of what many feared may be a looming ground invasion.
Tens of thousands of Israeli forces were deployed to battle holdout Hamas fighters in the south, where the bodies of civilians had been found strewn on roads and in town centres.
"The enemy is still on the ground," military spokesman Daniel Hagari said as a second night fell after the massive opening attack.
US President Joe Biden ordered "additional support for Israel in the face of this unprecedented terrorist assault by Hamas".
US Defense Secretary Lloyd Austin said Washington "will be rapidly providing the Israel Defense Forces with additional equipment and resources, including munitions".
Austin directed the USS Gerald R. Ford aircraft carrier and group of warships to the eastern Mediterranean, and said that Washington was augmenting fighter aircraft squadrons in the region.
Hamas has said the US aid amounted to "aggression" against Palestinians.
The conflict has had global impact, with several other countries reporting nationals killed, abducted or missing, among them Brazil, Britain, France, Germany, Ireland, Mexico, Nepal, Thailand and Ukraine.
A US National Security Council spokesperson confirmed that "several" Americans had been killed in the surprise attack, but did not provide further details.
Oil prices soared more than four percent Monday, sparking concerns about possible supply shocks from the crude-rich region.
Brent jumped 4.7 percent to $86.65 and West Texas Intermediate was up 4.5 percent at $88.39 in early Asian business.
- Abducted to Gaza -
Shock and dismay gripped Israel after at least 100 citizens were captured by Hamas and abducted into Gaza, with images circulating on social media of bloodied hostages.
Yifat Zailer, 37, said she was horrified to see online video footage from Gaza that showed her cousin and the woman's children, aged nine months and three years.
"That's the only confirmation we have," she told AFP, her voice breaking with emotion, and adding there was no information on her cousin's husband or her elderly parents.
"After the army took control of the kibbutz, they weren't at home," she said. "We assume they were kidnapped ... We want to know what their condition is, we want them to return safe. They're innocent civilians."
https://twitter.com/izainab_khn/status/1711181292052664348
Israel also came under attack from the north when Lebanon's Hezbollah launched guided missiles and artillery shells Sunday "in solidarity" with the unprecedented Hamas offensive, without causing any casualties.
Israel responded with artillery strikes across the UN-patrolled border.
"We recommend Hezbollah not to come into this," said army spokesman Richard Hecht. "If they come, we are ready."
Israel was stunned when Hamas launched their multi-pronged offensive on Saturday, the Jewish Sabbath, with at least 3,000 rockets raining down as fighters infiltrated towns and kibbutz communities and stormed an outdoor rave where many revellers were shot dead.
Panicked Israelis hiding in their homes told reporters that militants were going door to door and shooting civilians or dragging them away.
"Israel was caught flat-footed by the unprecedented attack," said Jonathan Panikoff, director of the Scowcroft Middle East Security Initiative. "I've heard multiple comparisons to 9/11, and many Israelis are struggling to understand how this could have happened."
- 'No respite' -
Western capitals have condemned the attack by Hamas, which Washington and Brussels consider a terrorist group.
Israel's foes have praised the assault, including Iran whose President Ebrahim Raisi voiced support when he spoke with the leaders of Hamas and the Islamic Jihad group.
Pro-Palestinian protests took place in the United States, Iraq, Pakistan and other countries, while Germany and France were among nations stepping up security around Jewish temples and schools.
In the Egyptian city of Alexandria a police officer opened fire "at random" on Israeli tourists Sunday, killing two of them and their Egyptian guide before he was arrested.
Netanyahu -- who leads a hard-right coalition government but has received pledges of support from political opponents -- has vowed to turn Hamas hideouts "to rubble" and urged Palestinians there to flee.
"We are embarking on a long and difficult war that was forced on us by a murderous Hamas attack," Netanyahu wrote on X, formerly Twitter.
Israeli attacks have reduced several Gaza residential towers to rubble and destroyed a mosque in Gaza's Khan Yunis as well as the central bank.
- 'We will not give up' -
Hamas has labelled its attack "Operation Al-Aqsa Flood" and called on "resistance fighters in the West Bank" and "Arab and Islamic nations" to join the battle.
Its attack came half a century after the outbreak of the 1973 conflict called the Yom Kippur War in Israel, sparking bitter recriminations for what was widely seen as an enormous intelligence failure.
"There was a very bad failure here," said Sderot resident Yaakov Shoshani, 70. "The Yom Kippur War was small compared to it, and I was a soldier in the Yom Kippur War."
He recalled the terror of the attack on their town near Gaza.
"I held a kitchen knife and a large screwdriver, and I told my wife that, if something happens, to make sure to read the Kaddish (prayer) over me, if you stay alive," he said. "And so we stayed close to each other at home, shut everything and turned off the lights."
https://twitter.com/highhmaria/status/1711216555881599110
Hamas chief Ismail Haniyeh has predicted "victory" and vowed to press ahead with "the battle to liberate our land and our prisoners languishing in occupation prisons".
An Israeli survivor of the attack on Sderot, Yitzhak, 67, said he now expected the army to "conquer Gaza house by house, clean the area there properly, and not leave Gaza until they get the very last rocket out of the ground."
Many Gaza residents voiced defiance.
"We will not give up, and we are here to stay," said Mohammed Saq Allah, 23. "This is our land, and we will not abandon our land."