Hospitals in London have had to cancel cancer operations this week because of a Russian cyber-attack that continues to cause serious disruption to NHS services in the capital. St Thomas’ and King’s College hospitals have postponed procedures that their surgeons were due to perform on cancer patients since the attack began last Monday, the Guardian can reveal. They have been forced to take the step because the hack meant they would not have been able to provide a blood transfusion for any patient who needed one. Russian hackers, thought to be the Qilin group, launched a ransomware attack on Synnovis, which supplies blood tests to St Thomas’, King’s and other hospitals in south-east London. One senior NHS manager told the Health Service Journal (HSJ) that the attack, one of the biggest to hit the service, was “everyone’s worst nightmare”. NHS England has released few details of the impact of the cyber-attack, despite the fact that it continues to cause major disruption for six NHS trusts and dozens of GP practices in south-east London that between them provide care to about 2 million people. It refused on Friday to say how many operations, including cancer and transplant surgeries, had been put off this week as a result of the attack. Officials maintained that they did not have figures for the number of operations affected, even though managers in the hospitals involved have had to explain to patients why their procedures have been delayed. In a statement on Thursday NHS England said only that “some non-urgent operations and procedures including transplants” were being postponed. Dr Chris Streather, the medical director for NHS England’s London region, said in the statement: “We are sorry to all those who have been impacted and staff will work hard to re-arrange appointments and treatments as quickly as possible.” The same statement disclosed for the first time that no fewer than six NHS trusts – four more than NHS England initially reported – had been affected. They include the South London and Maudsley and Oxleas mental health trusts, Lewisham and Greenwich acute trust and Bromley community services trust, as well as the very large acute trusts that run King’s and St Thomas’. The lack of transparency is causing unease among staff affected by the cyber-attack, which the HSJ reported was likely to keep causing problems for “weeks, not days”.