A vigil for the more than 100 people who remain unaccounted for after being kidnapped by Hamas in October has taken place in central London. Tuesday’s event, which was organised by groups including the Board of Deputies of British Jews and the Jewish Leadership Council, was addressed by family members of the hostages and Jewish religious figures. Six months have passed since 1,200 people were killed and about 250 people taken hostage by Hamas, a proscribed terrorist group, on 7 October – the largest loss of Jewish life in a single day since the Holocaust. About 129 hostages remain unaccounted for, with at least 34 of them presumed to be dead. The attack triggered Israel to launch a military offensive in Gaza, where more than 32,000 people have been killed. About 300,000 Gazans are facing famine, according to the UN. Ayala Harel – the niece of a hostage, Michel Nisenbaum, 59 – attended the vigil. Nisenbaum, who suffers from Crohn’s disease, is a Brazilian-Israeli citizen and has lived in Israel for 45 years. Harel, 42, who survived the Hamas attack, told the Guardian at the vigil: “I’m still at 7 October, it’s a nightmare. We are living in hell. It’s very difficult.” Harel described her mother’s only brother as a “wonderful person … if you asked him something, he would never say no”, adding that he “adores” his two daughters and six grandchildren. “He has a grandson that he’s never met, his daughter gave birth four months ago,” she said. Harel added that her uncle does not have medicine to treat his Crohn’s disease, saying: “If he’s alive, he’s probably dying, you can’t live with Crohn’s without treatment.” She said the family was “running out of time” and called for the British government to mediate for a hostage deal “to bring our love[d ones] back home”. Chief rabbi Ephraim Mirvis also addressed the vigil. “How different this Passover will be, from all other Passovers,” he said. “As we approached other Passovers we’ve been filled with happiness and joy … but as we approach this Passover, we are filled with sorrow and concern. “Sorrow over everything that has happened since 7 October and deep concern for the future … We pray for peace, for the wellbeing and security, one and all.” The brother of a British woman who was killed when Hamas stormed their home in the Be’eri kibbtuz in southern Israel also addressed the vigil. Stephen Brisley’s sister, Lianne Sharabi, and his nieces – Noiya, 16, and Yahel, 13 – were murdered in the 7 October attacks. Brisley called for a deal earlier this year to enable the release of the hostages, including his brother-in-law, Eli Sharabi. He described his brother-in-law at the vigil, who “talks about the weather just like a Brit – because he is us and we are him”. Brisley added: “Eli is, unfortunately, a Manchester United fan … I felt his absence keenly over the past couple of weeks when Manchester United played my team, Liverpool. It’s those silly little things we miss. “It’s been incredibly humbling to experience the sense of community among Jews and Israelis based in the UK since the events of 7 October,. I’ve learned that, such is that sense of community and togetherness, barely an Israeli or Jew seems to have been left untouched by the horror of that day.” Brisley’s speech provoked tears among those at the vigil, some of whom held Israeli flags and images of people held hostage in Gaza. A chant of “ “bring them home” was called out at regular intervals. Talks have been held in Cairo, mediated by the US, Qatar and Egypt, on an immediate ceasefire and the release of the hostages. However, there is increasing frustration at the delays in securing a deal. Tens of thousands of Israelis took part in anti-government protests in Tel Aviv last weekend demanding a hostage deal. Benjamin Netanyahu, the Israeli prime minister, has said the war will not end until there is “complete victory over Hamas” and all hostages have been returned. Hamas rejected the latest ceasefire proposal, claiming it does not meet any Palestinian demands. The location of the London vigil was not released publicly on the advice of the Metropolitan police, the Board of Deputies of British Jews said. The Community Security Trust, a charity that aims to protect British Jews from antisemitism, also attended.