The Israeli death toll after the surprise attack by the militant group Hamas on communities in the country’s south has risen to at least 700, including 44 soldiers, as the prime minister, Benjamin Netanyahu, said Israel was embarking on a “long and difficult war”. In Gaza, which was pummelled by Israeli airstrikes, officials reported at least 413 deaths. With thousands of Israelis and Palestinians wounded since Saturday morning, Israel said more than 100 Israeli citizens, including women and children, were believed to have been abducted at gunpoint by Hamas to Gaza. At least 260 bodies were discovered at the site of a music festival in a desert kibbutz. Many of the Israeli victims were civilians who were murdered in their homes, on the streets of their communities and at other locations along a broad swathe of territory bordering Gaza, leading the US secretary of state, Antony Blinken, to describe the Hamas assault as an “indiscriminate terrorist attack”. Blinken added that Washington had not seen any evidence that Iran was behind the attack. In a call to Netanyahu, Joe Biden said US military assistance was “now on its way to Israel with more to follow over the coming days”. The US defence secretary, Lloyd Austin, said the USS Gerald R Ford aircraft carrier and its strike group of warships would be moved closer to Israel in the Mediterranean while US air force squadrons in the region would be reinforced in a show of strength. As Israel’s security cabinet signed off on a wide-ranging authorisation for military action, Israelis were struggling to comprehend the scale of Saturday’s attack, as the likelihood of a ground invasion of Gaza and a wider conflagration with Hezbollah in Lebanon loomed large. On Sunday afternoon waves of Israeli jets were carrying out “intense” strikes on targets in Gaza. Dozens of Israeli armoured vehicles and tanks were heading towards Gaza, suggesting preparations were under way for a ground offensive. In a televised address on Saturday night, Netanyahu said the Israeli military would use all of its strength to destroy Hamas’s capabilities in response. “Get out of there now,” he told people in Gaza, who have no way to leave the tiny, overcrowded Mediterranean territory. The number of Israeli dead climbed sharply on Sunday as Israel’s forces secured areas that had been briefly seized by Hamas militants in the country’s south, and emergency workers uncovered scores of bodies. At an emergency reception centre for desperate families of the missing at Ben Gurion airport, Nava Avadia, 60, said her son Etai Hadar, 27, was at a party when the attacks took place. “His girlfriend managed to make a call to her sister saying they escaped into the kibbutz from the field where the party was, but since then we have heard nothing. “We hope it is just they have no battery. We have no idea. We pray for good news. The army won’t let us go down there.” The growing list of the dead represented every corner of Israeli society including a commando general, a former Israeli international football player, partygoers and families, including women and children. As Israel struck 800 targets in Gaza, the official toll of Palestinians killed there rose to more than 400 including 20 children, with close to 2,000 people wounded. At a UN-run school in Gaza City’s north-western Sheikh Radwan neighbourhood, residents described overnight Israeli strikes that hit the school’s courtyard, causing panic and light injuries among those sheltering there. At another school serving as a shelter in central Gaza City, people were piling up blankets and food in the three-storey building. New arrivals brought in mattresses, packing their children into small and crowded classrooms. “We didn’t know where to go,” said Umm Muhammad, a resident of a district on the eastern borders of Gaza. She described waking up in the middle of the night to screams, strikes and calls for evacuation. “We arrived at the schools miraculously, because there was no transport.” Israel announced on Sunday it had ordered the evacuation of communities bordering Gaza, while thousands of reservists reported for duty and more received call-ups as a state of emergency was expected to be formalised on Monday. Israel’s war aims remained unclear on Sunday, including whether it would seek to remove Hamas from power in Gaza, and how long any operation might last. Yohanan Plesner, the head of the Israel Democracy Institute, said the declaration of war was largely symbolic, but “demonstrates that the government thinks we are entering a more lengthy, intense and significant period of war”. Underlining the international alarm over the escalating events, Poland announced it would send military planes to evacuate its citizens from Israel. While the Israel Defence Forces (IDF) said they had retaken control of more than 20 locations attacked by Hamas, fighting reportedly continued in Kfar Aza where gunmen belonging to the militant Islamist group were said to be holed up. As the UN security council prepared to go into an emergency session later on Sunday and the UN secretary general, António Guterres, urged “maximum restraint”, the Iranian-backed armed group Hezbollah said it had fired rockets and artillery into northern Israel “in solidarity” with the Palestinian people. Israeli forces responded with artillery strikes on Lebanon and a drone attack on a Hezbollah post near the border, the military said. Later on Sunday afternoon, people in northern Israel reported interceptions by a Patriot missile battery. There were also reports on Sunday afternoon that Israel was preparing to evacuate communities along the Lebanon border. As the scale of the deaths and injuries on both sides of conflict became apparent, the Israeli police service alone said it had lost 30 officers in the first day of fighting, while the Shin Bet domestic security agency said five of its members had been killed. As relatives of missing Israelis gathered at hospitals and made online appeals, the Israeli military opened a call centre for families of “unresponsive” soldiers seeking information about their fate. Among those listed among the dead on the IDF memorial page was Amir Fisher, a general in a commando brigade. Hezbollah said in a statement that its rocket and artillery attacks had targeted three posts including a “radar site” in the Israeli-occupied Shebaa Farms, a slice of land occupied by Israel since 1967 that Lebanon claims. Meanwhile, in neighbouring Egypt a police officer shot dead two Israeli tourists and an Egyptian at a tourist site in Alexandria, the country’s interior ministry said. On Saturday, backed by a barrage of rockets, hundreds of Hamas operatives broke out of Gaza and fanned out into 22 Israeli towns, shooting at civilians in an attack that stunned Israel. Video footage showed several people being abducted by gunmen. In some places, militants roamed for hours, targeting civilians and soldiers, as Israel’s military scrambled to muster a response. Early on Sunday, the Israeli military said its forces were still fighting incursions by the militant group in eight places, and that two hostage situations had been “resolved”, but did not clarify whether all the hostages had been rescued alive. Survivors of the Hamas assault in various locations described playing dead under the bodies of family members or fleeing through fields from gunmen on motorbikes pursuing attendees at a rave near the border. As Israel prepared for a substantial ground invasion of Gaza, the Israeli cabinet announced it had cut off all electricity, fuel and goods going into Gaza. In his televised address on Saturday night, Netanyahu, who had earlier declared Israel to be at war, said the military would use all of its strength to destroy Hamas’s capabilities and “take revenge for this black day”. He said: “This war will take time. It will be difficult.” “All the places that Hamas hides in, operates from, we will turn them into rubble,” he added. Hamas and Israel have already fought four wars since the group took over the strip in 2007. Much of Gaza was thrown into darkness by nightfall after electricity from Israel, which supplies almost all of the territory’s power, was cut off earlier in the day. The Hamas incursion fell on Simchat Torah, a normally joyous day when Jews complete the annual cycle of reading the Torah scroll. Several airlines have cancelled flights into Israel and the Federal Aviation Association issued a warning to US pilots to use caution over Israeli airspace. Biden said on Saturday he had spoken to Netanyahu to say the US “stands with the people of Israel in the face of these terrorist assaults. Israel has the right to defend itself and its people, full stop”. Saudi Arabia, which has been in talks with the US about normalising relations with Israel, called on both sides to exercise restraint. The kingdom said it had warned repeatedly about the danger of “the situation exploding as a result of the continued occupation [and] the Palestinian people being deprived of their legitimate rights”.