Major London hospitals canceled some operations on Tuesday after a cyber-attack on a key service supplier had a "major impact", particularly on blood transfusions, according to internal memos posted on social media.

The attack on pathology partner Synnovis hit King's College Hospital and Guy's and St Thomas' in the center of the British capital.

"I can confirm that our pathology partner Synnovis experienced a major IT incident earlier today, which is ongoing," Ian Abbs, CEO of Guy's and St Thomas NHS Foundation Trust, wrote in the memo.

"This is having a major impact on the delivery of our services, with blood transfusions being particularly affected.

"Some activity has already been canceled or redirected to other providers," he added.

The Health Service Journal (HSJ) trade publication reported that the system was the victim of a ransomware attack, citing senior sources.

One of the sources said it could take "weeks, not days" to access pathology results.

© 2024 AFP