Hospitals across England canceled appointments and turned away patients Friday after suffering an apparent cyberattack.

Hospitals in London, northwest England and other parts of the country reported problems with their computer systems. They asked patients not to come to the hospitals unless it was an emergency.

Pictures posted on social media showed screens of NHS computers with images demanding payment of $300 worth of the online currency Bitcoin, saying: “Ooops, your files have been encrypted!”

NHS Merseyside, which operates several hospitals in northwest England, tweeted that “following a suspected national cyberattack, we are taking all precautionary measures possible to protect our local NHS systems and services.”

East and North Hertfordshire NHS Trust, which runs hospitals in an area north of London, said “the trust has experienced a major IT problem, believed to be caused by a cyberattack.”

It said its hospitals had shut down all computer systems as a protective measure and canceled all non-urgent activity.

Bart’s Health, which runs several London hospitals, said it had activated its major incident plan, cancelling routine appointments and diverting ambulances to neighboring hospitals.

Britain’s National Health Service is a source of pride for many Britons but faces substantial budget issues.

(AP)