The Israeli prime minister, Benjamin Netanyahu, has announced an emergency wartime government, as pressure mounts for the establishment of corridors to allow aid and medicine into the Gaza Strip and to allow civilians to leave. Benny Gantz, a senior opposition figure and former defence minister, joined the government for the duration of the conflict. Netanyahu, Gantz and Yoav Gallant, the defence minister, are forming a “war cabinet” as Israeli troops continued to build in the south of the country in preparation for an expected ground invasion. In a televised address late on Wednesday, Netanyahu described atrocities that took place during the weekend attack by Hamas militants, who he said shot children in the head, burned people alive, raped women and beheaded soldiers. “Every Hamas member is a dead man,” he said. “We will crush and destroy it.” Netanyahu’s extreme rightwing coalition partners will continue to serve in the government. The country’s chief opposition leader, Yair Lapid, was invited to join the new cabinet but did not immediately respond to the offer. Inside Gaza, the enclave’s sole power station ran out of fuel, adding to the looming catastrophe particularly for hospitals. “Soon all services vital for the survival of the population, including hospitals, will no longer function,” said the Mezan centre for human rights in Gaza. Mahmoud Matar, a surgeon in Gaza, said hospitals were “completely overwhelmed with the number of injuries and the number of dead”. He told the BBC: “The smell of death is all around now in Gaza. There is no water, there will be no electricity, and we have very bad network connection. I am currently looking for water to drink.” Joe Biden described the assault on Israel by Hamas as “the deadliest day for Jews since the Holocaust during a round table of Jewish leaders in Washington on Wednesday evning . The US president said Saturday’s attack was “sheer evil” and a “campaign of pure cruelty against the Jewish people”. “Silence is complicity,” Biden said. “I refuse to be silent”. He said he had spoken again today with Netanyahu and that the US is “surging” additional military assistance to the Israel Defense Forces. “This attack was a campaign of pure cruelty, not just hate, but pure cruelty, against the Jewish people,” Biden said, adding: “I never really thought that I would see, have confirmed, pictures of terrorists beheading children.” The UN humanitarian agency OCHA described a “mass displacement” in the Gaza Strip, with more than 263,000 people fleeing their homes. It said that number was expected to rise further. The death toll that began in Saturday’s carnage, carried out by Hamas militants and airstrikes on Gaza by Israeli forces, rose again. Israel said 1,200 people had been killed and more than 2,700 injured as bodies were still being recovered from towns and communities near the Gaza border. Israel believes Hamas is holding about 150 Israeli hostages inside Gaza. The Gaza health ministry said about 1,100 Palestinians had been killed and 5,339 wounded in airstrikes on the crowded enclave in the past five days. Antony Blinken, the US secretary of state, was due to fly to Israel on Wednesday to show solidarity with its ally and to discuss military support. The US has been involved in discussions about a safe passage to allow civilians in Gaza to leave to blockaded territory, now under intense bombardment. The border crossing between Gaza and Egypt has been closed since the conflict began. In comments that are potentially extremely damaging for Netanyahu, a senior Republican said a warning of potential violence came three days before the attack. “We know that Egypt has warned the Israelis three days prior that an event like this could happen,” Michael McCaul, the chair of the powerful US House foreign affairs committee, told reporters after a closed-door intelligence briefing for lawmakers on the crisis. “I don’t want to get too much into classified but a warning was given. I think the question was at what level,” he said. The attack may have been planned as long as a year ago, McCaul said. “We’re not quite sure how we missed it. We’re not quite sure how Israel missed it.” Sirens sounded across the south and the north of Israel on Wednesday. The Israeli military said hostile aircraft had entered the country from Lebanon, and urged citizens to take shelter. Some reports suggested drones or hang-gliders had been deployed by Hezbollah militants. Earlier, Hezbollah fired anti-tank missiles at an Israeli military position, claiming to have killed and wounded troops. The Israeli military confirmed the attack but did not comment on possible casualties. The Israeli army shelled the area in southern Lebanon where the attack was launched. António Guterres, the United Nations secretary general, said a spillover of the conflict in Israel must be avoided and that he was concerned about reported attacks from southern Lebanon. “I appeal to all parties, and those who have an influence over those parties, to avoid any further escalation and spillover,” he said. Meanwhile, British Airways and Virgin Atlantic became the latest carriers to announce they were suspending all flights to and from Tel Aviv, citing security concerns. The BA announcement came after the captain of a flight approaching the airport turned back to Heathrow. A spokesperson for Israel’s airports authority said rockets were flying around Tel Aviv at the time but were not an immediate threat to the flight or to the airport. James Cleverly, the UK foreign secretary, was forced to take shelter while visiting Ofakim, a community in southern Israel. Cleverly flew to Israel to demonstrate the UK’s “unwavering solidarity”. Lt Col Jonathan Conricus, a spokesperson for the Israel Defence Forces, said on Wednesday morning that 300,000 reservists had been sent south, close to Gaza, and were getting ready “to execute the mission we have been given by the Israeli government … to make sure that Hamas, at the end of this war, won’t have any military capabilities by which they can threaten or kill Israeli civilians”. Hamas launched its surprise attack on Israel on Saturday morning, firing thousands of rockets and breaching the hi-tech security fence around Gaza to allow hundreds of militants to cross into Israel. Israelis, including the very old, the very young and at least 260 people at a music festival in the area, were killed in scenes of horror that have shocked the world. On Wednesday it was confirmed that the dead included Jake Marlowe, a 26-year-old British man who had been working on the festival’s security team. His parents said they were heartbroken.