Israel is believed to have identified most of the hostages abducted by the militant group Hamas and has started notifying their families. Officers from the Israel Defence Forces were to tell about 100 families on Tuesday that their loved ones were in Gaza, the Times of Israel reported, citing Israeli army radio. For some, the notifications will merely confirm what they already know from recognising relatives in harrowing footage of people – some bleeding and visibly terrified – being dragged into the Palestinian enclave after Hamas’s lightning attacks last weekend. The videos were filmed by Hamas and shared on social media and through WhatsApp groups. Gilad Erdan, Israel’s ambassador to the United Nations, said the total number of hostages seized was between 100 and 150. The hostages’ fate is unclear. Israeli airstrikes have pounded Gaza in intensive waves every four hours, reducing apartment blocks to rubble. Gaza’s health ministry said at least 770 Palestinians had died and 4,000 were wounded. On Monday Hamas said airstrikes had killed four hostages and their captors. The Qassam brigades, the armed wing of Hamas, have threatened to execute one hostage for each new Israeli airstrike on civilian targets without warning. Israel said on Monday it would cut off electricity, food, fuel and water in a “complete siege” of the tightly packed strip of 2.3 million people. Authorities said more than 1,000 Israelis died in the Hamas attacks. Uncertainty over the hostages is an acute dilemma for the Israeli military as it plans a possible ground offensive in Gaza and is an agonising ordeal for the hostages’ relatives. Yossi Sneider told the BBC of his horror after seeing a picture of his cousin Shiri Bib and her two children, four-year-old Ariel and nine-month-old Kfir, surrounded by militants. Later in a video he said he saw Bib crying and holding her children. Bib, a kindergarten teacher who had been living in a kibbutz, was gentle and kind, said Sneider. “She doesn’t deserve this experience; nobody does. I have no words to describe this.” Bib’s parents, Margit and Yossi Silverman, and her husband, Yarden, were also missing, he said. Margit has Parkinson’s and diabetes. Uncertainty is tormenting relatives. Jennifer Damti said she had not slept since learning that her daughter Kim Damti, 22, an Irish-Israeli citizen who attended the Supernova festival, was missing. “All I can think about is where she is, if she’s suffering, if she’s still alive, I just want her back,” Damti told ABC News. Qatar is reportedly attempting to broker an agreement for Hamas to release Israeli women and children in exchange for Israel freeing 36 Palestinian women and children from Israeli prisons. Several foreign nationals are feared to have been taken hostage, including at least two Mexicans, three Brazilians and an unknown number of US citizens. The Israeli military said it had set up a situation room to collate and track information about the hostages, who include soldiers. Police and the army’s Home Front Command have also established a situation room to identify those killed in Hamas attacks. People with missing relatives queued outside a police station to supply DNA samples and other means to facilitate identification, the Times of Israel reported.