Up to 10 Britons are being held hostage by Hamas in Gaza, the foreign secretary has said, higher than previous informal estimates. Israel estimates that 126 people from different countries are being held hostage, with reports previously suggesting six of those taken were British. Up to 17 British people, including children, are thought to be dead or missing since the conflict began last weekend. The UK has left it to hostages’ relatives to decide whether to reveal the identity of those captured, but its typical advice to families caught up in such situations is not to publicise cases as it may increase the value of the hostage to their captors. Speaking on Sunday to Sky News, James Cleverly described the suggestion that 10 British people were being held as “not an unreasonable estimate”. One source said it was not possible to be absolutely precise because Qatar, which has been acting as the chief intermediary with Hamas over the hostage crisis, has not been given a definitive list, and that it was possible someone had been captured without the Foreign Office being briefed. The UK has no direct diplomatic contact with Hamas, but has intermediaries including through Qatar and Iran. On Sunday, in an indication of the challenge of providing accurate estimates, the Israel Defence Forces revised down the total number of Israeli and foreign hostages from 150 to 126. Israeli authorities have indicated they are willing to launch attacks on Gaza even if hostages are in harm’s way. However, the mood inside Israel is febrile and the prime minister, Benjamin Netanyahu, is aware he is also being lobbied by families to make the hostages a priority. Separately, the UK Foreign Office has said it is doing all it can to help Britons trapped in Gaza to escape, but Cleverly said it was proving “incredibly difficult” to open the Rafah border crossing into Egypt. He said he had spoken to his Egyptian counterpart, adding: “We stay in very close coordination with the United States of America, with other friends in the region and of course with the Israeli government trying to coordinate a time window when the Rafah crossing can be opened so that people can leave.” “That is proving incredibly difficult, so I’m not able to say with any certainty when that crossing may be open.” The UK has close business ties with Egypt, and the prime minister, Rishi Sunak, spoke last Wednesday with the Egyptian president, Abdel Fatah al-Sisi, to offer help to open the Rafah crossing.