Hamas has said that 250 people are being held hostage in Gaza, and that they will be released “when conditions are ripe”. In a televised statement late on Monday, Abu Ubaida, the spokesperson for Hamas’s military wing, said the Izz ad-Din al-Qassam brigades had been holding 200 people captive since the Hamas raid on 7 October. He said about 50 others were being held by other “resistance factions and in other places” and claimed that at least 22 hostages had been killed in Israeli airstrikes on Gaza. Earlier on Monday, the Israeli military said Hamas was holding 199 hostages in Gaza, and that all families had been notified of their identities. The number has risen sharply in the past day. On Sunday, a figure of 126 was given that was later updated to 155. “We are making valiant efforts to try to understand where the hostages are in Gaza, and we have such information,” said an Israeli military spokesperson, Daniel Hagari. “We will not carry out an attack that would endanger our people.” The hostages are believed to be mostly civilians, ranging from babies to people in their 80s. Many have dual nationality. The UK has said 10 of its nationals are missing, although some of those are feared to be dead. There are thought to be about 20 US citizens held hostage in Gaza. The presence of hostages in the strip has complicated Israel’s plans for a ground invasion of the narrow coastal territory that is home to 2.3 million people. Hamas has warned that it will kill hostages in response to unannounced Israeli strikes on civilian targets. On Friday, it was reported that Israeli troops had retrieved an unspecified number of bodies of hostages during “localised raids”. The Hostages and Missing Families Forum is supporting relatives and friends, publicising the plight of the hostages and demanding action. About 100 volunteers, including former diplomats, communications experts and former soldiers, are pooling their expertise. The Israeli public has rallied behind hostages before, but never on this scale. The family of Gilad Shalit, a young soldier held hostage in Gaza for five years, camped outside the prime minister’s residence in Jerusalem. Noam Shalit, the soldier’s father, who died last year, lobbied politicians relentlessly for his son’s release, going on hunger strikes, touring television studios, organising marches and protests, and distributing hundreds of thousands of car bumper stickers. Campaigners for the hostages have posted pictures and biographies of the captives on social media and are demanding regular meetings with government and military officials. The forum has asked the International Committee of the Red Cross to negotiate humanitarian access to the hostages. The group has met Gal Hirsch, an Israeli army general put in charge of the hostage issue by the prime minister, Benjamin Netanyahu. Some relatives have claimed that information has been withheld from them. Among those believed to be held in Gaza are Vivian Silver, 74, a well-known peace activist, the co-founder of Women Wage Peace and a former board member of the human rights organisation B’Tselem, who lived in Be’eri, a kibbutz near the Gaza frontier. Another is Oded Lifshitz, 83, a veteran journalist who worked for decades for peace and the recognition of Palestinian rights. He was taken with his wife, Yocheved, 85, from their home in the Nir Oz kibbutz. Noam Alon, whose girlfriend, Inbar Haiman, went missing from the Supernova music festival on 7 October, said Israel’s political and military leaders “need to do all they can to free the hostages, alive and safe” before any ground invasion of Gaza. Haiman, 27, had been seen being driven away on a motorbike. Hamas later posted a video showing her being held by four Hamas men, said Alon. “Inbar is very clever and sensitive. I’m sure she will know that everyone is doing everything they can to get her out. She needs to stay strong and positive, and know this will end and she’ll be with us again.” The memory of Gilad Shalit’s captivity was vivid for Israelis, he said. “We don’t know if she’s being held alone or with others, or if she can even see the sunlight. But we are trying to be optimistic and do everything we can to bring her home.” Friends of Haiman, a graphic design and arts student in Haifa whose street art name is Pink, had created murals and graffiti to spread awareness of her plight. “Soon everyone will know about Inbar,” said Alon. In Jerusalem, Cardinal Pierbattista Pizzaballa, Pope Francis’s representative in the Holy Land, said he was willing to exchange himself for Israeli children taken hostage by Hamas. “I am ready for an exchange, anything, if this can lead to freedom, to bring the children home. No problem. There is total willingness on my part,” said Pizzaballa, the patriarch of Jerusalem.