Hosptials across the UK have been hit by what appears to be a major, nationwide cyber-attack, resulting in the loss of phonelines and computers, with many hospitals going "dark" and some diverting all but emergency patients elsewhere. At some hospitals patients are being told not to come to A&E with all non-urgent operations cancelled, the BBC reports.

The UK National Health Service said: “We’re aware that a number of trusts that have reported potential issues to the CareCERT team. We believe it to be ransomware.” It added that trusts and hospitals in London, Blackburn, Nottingham, Cumbria and Hertfordshire have been affected and are reporting IT failures, in some cases meaning there is no way of operating phones or computers.

At Lister Hospital in Stevenage, the telephone and computer system has been fully disabled in an attempt to fend off the attack.

NHS England says it is aware of the issue and is looking into it.

According to the Telegraph, doctors across the country have seen this message - what appears to be ransomware - flash up on their screens. The notification demands that $300 worth of bitcoin be sent to a specific address to unlock the infected computer.

One source told Health Service Journal that multiple trusts had been affected by a suspected malware attack around 1.30pm. They said trusts had their computer systems almost entirely shut down.

East and North Hertfordshire NHS trust said in a statement: “Today the trust has experienced a major IT problem, believed to be caused by a cyber attack.

“The trust is postponing all non-urgent activity for today and is asking people not to come to A&E - please ring NHS111 for urgent medical advice or 999 if it is a life-threatening emergency. “To ensure that all back-up processes and procedures were put in place quickly, the trust declared a major internal incident to make sure that patients already in the trust’s hospitals continued to receive the care they need.”Health officials are understood to have declared a major incident and ordered a meeting of national resilience teams. NHS Digital said: “We’re aware that a number of trusts that have reported potential issues to the CareCERT team. We believe it to be ransomware.”

Routine appointments are being cancelled at Barts and other hospitals. Ambulances diverted. Major incidents being declared. — Shaun Lintern (@ShaunLintern) May 12, 2017

There are reports that trusts affected include East and North Hertfordshire, North Cumbria, Morecambe Bay hospitals, Blackpool, and Barts Health in London. A number of GP surgeries also say they are also unable to use their systems.

IT specialists are working to resolve the problem as quickly as possible, a statement from the trust says. A GP from a surgery in York said: "We received a call from York CCG [Clinical Commissioning Group] around an hour ago telling us to switch off all of our computers immediately. "We have since remained open, and are dealing with things that can be dealt with in the meanwhile."

Services affected are thought to include picture archiving communication systems for x-ray images, pathology test results, phone and bleep systems and patient administration systems. The source added: “This will mean delays and a focus on the sickest patients. I’ve seen it once before and we relied on local trusts supporting each other. If truly widespread then that’ll not be an option.”