The loss of power, after a blockade imposed by Israel, came as its last power station ran out of fuel. Supplies of food, water and medicine were also dwindling.

Israeli Prime Minister Benjamin Netanyahu said this evening that Hamas militants had beheaded soldiers and raped women in its attack on Saturday.

In a late televised address, Mr Netanyahu also said that Israel would "crush and destroy" Hamas in response.

The Israeli prime minister added that every Hamas member was a "dead man".

Mr Netanyahu also detailed what he said were some of the atrocities that took place after Hamas militants crossed the border into Israel.

He said boys and girls were shot in the head and that people had been burned alive.

Israel warns citizens after 'hostile aircraft' flies over from Lebanon - follow live conflict updates

In other key developments:
• 17 British nationals, including children, killed or missing, Sky News understands
• Missing Irish-Israeli woman confirmed dead
• Met Police appeals for people to send them footage of attacks in Israel
• 22 Americans have been killed, US state department says
• Netanyahu and opposition agree to form emergency government
• UK foreign secretary runs for cover during Israel visit
• At least 1,200 Israelis dead and more than 2,700 injured, IDF says
• At least 1,100 Palestinians dead and 5,184 injured in Israeli strikes, Gaza Health Ministry says
• UK royals issue statements in solidarity with Israel

Israel strikes neighbourhood '450 times in 24 hours'

Earlier, the Israeli Defence Forces (IDF) rowed back on its earlier warning that a "hostile aircraft" had entered its airspace from Lebanon.

The Israeli Home Command had told people in the north of the country to stay at home and lock their doors due to a "possible infiltration".

However, an IDF spokesman has now said air raid alerts that were sounded may have malfunctioned.

It comes after Israeli warplanes bombed the Palestinian territory overnight and into Wednesday, reducing buildings to rubble and reportedly striking 450 targets in the al-Furqan neighbourhood of Gaza in 24 hours.

11 UN refugee agency workers killed

Hamas's armed wing, meanwhile, says it was carrying out "major strikes" on the southern Israeli city of Ashkelon, claiming it is "in response to the continued displacement of civilians".

A hospital in Ashkelon has said a rocket hit their building, while the IDF said sirens had sounded in the city without offering further details.

With Israel continuing its "total siege" to stop the entry of food, fuel and medicines into Gaza, the city of 2.3 million people has been left without electricity after its sole power station ran out of energy.

Jalal Ismail, from Gaza's energy authority, had said power would run out in the city by midday on Wednesday.

"The power plant will stop working completely today at 2pm (12pm UK time), due to the exhaustion of the amount of fuel needed to operate it," he said.

Meanwhile, the UN's Palestinian refugee agency confirmed 11 of its workers have been killed in Israeli airstrikes on the Gaza Strip since Saturday.

The UN Relief and Works Agency (UNRWA) which said some of them were "killed in their homes with their families".

UNRWA did not specify if those killed were Palestinian or foreign personnel.

Among the dead are five teachers, one engineer, one psychological counsellor and three support staff.

UNRWA also said nearly 175,500 internally displaced people were sheltering in 88 of its schools across Gaza.

Meanwhile, the International Federation of Red Cross and Red Crescent Societies (IFRC) said in a separate statement that five of its members - four in Gaza and one in Israel - had been killed in the conflict.

IFRC said that four Palestine Red Crescent paramedics were killed when their ambulances were hit in two different incidents on Wednesday.

On Saturday, an ambulance driver for Magen David Adom, Israel's national emergency service, lost his life while driving an ambulance to treat the injured, IFRC said.

Saudi Arabia speaks with Iran about 'need to end war crimes'

Meanwhile, Saudi Crown Prince Mohammed bin Salman has stressed in a phone call with Turkey's president that the kingdom is making efforts to stop the escalation in the conflict, the Saudi state news agency has said in a statement.

The crown price also asserted the need to stop the Israeli attack on the Gaza Strip and stressed the kingdom's firm position towards supporting the Palestinian cause, the news agency added.

Prince Mohammed also spoke with the Iran's president as the pair discussed the "need to end war crimes against Palestine".

The attack by Hamas comes weeks after Mr Netanyahu told the United Nations General Assembly his country was on the cusp of a historic peace deal with Saudi Arabia.

Hamas and Iran were strongly opposed to the growing prospect of the peace deal between the two nations.

King expresses shock at 'barbaric' attacks

It comes as British Foreign Secretary James Cleverly is on a visit to southern Israel where he was seen running for cover as air sirens blared in the city of Ofakim.

The Israeli foreign ministry said the siren was warning citizens of incoming Hamas rocket fire.

Mr Cleverly is on the visit to show the UK's support for Israel and plans to meet survivors.

The trip is taking place on the same day King Charles held a call with Israel's president to express his "deep shock" at the "barbaric" attacks launched by Hamas.

Isaac Herzog thanked the King for his support and said his words were an "important statement and of great comfort" to the people of Israel.

"The two talked at length about the terrible massacre and how it was carried out," a statement from Mr Herzog's office said.

The conflict is into its fifth day as Israel said it is shifting all schools to remote learning from Sunday and stepping up issuing firearms to licensed citizens.

In another sign of the crisis widening, the conflict also spread further afield once again - with the Hezbollah militant group claiming responsibility for a rocket strike on Israeli territory launched from Lebanon in the morning.

The group said it fired precision missiles in response to Israeli attacks that left three of its fighters dead earlier in the week.

Hitting back, the IDF confirmed it was striking Lebanese territory in response to what it thought was an "anti-tank weapon" across the border and said it had hit a Hezbollah lookout position.

To bolster its armoury, Israel received a delivery of "advanced weaponry" from the US, described as an "initial shipment" by the ministry of defence.

The US has also sent a team of technical experts to Israel to assist in hostage recovery, with Hamas keeping dozens of Israelis captive.

President Joe Biden said his administration would "surge" supplies into Israel, but did not provide any specifics on what was being sent.

While Israel has vowed to "wipe out" Hamas and further signs on Wednesday suggest a ground offensive is in the works, the US reportedly wants to create a humanitarian corridor for Gaza.

With residents in Gaza trapped between Israel, a closed Egyptian border and the sea, NBC News reports the Biden administration is coordinating with other countries on a plan offering civilians escape.