- Ransom was demanded to unlock files that were 'encrypted' by the attack
- The demand specifies that payment should be made via bitcoin
- The attack may have broader implications beyond England's health service
The BBC broadcast a screen-shot of a message apparently sent to the National Health Service medical facilities demanding ransom for the unlocking of computer files that had been "encrypted" by the attack.
The demand specifies that payment should be made via bitcoin, an online currency.
The message's authenticity could not be independently verified.
A statement from NHS Digital - the computer services arm of the health service - said at least 16 hospitals or doctor's offices had been directly affected by the attack.
Other health-care centers, meanwhile, turned off their computers to avoid potential infiltration.
NHS Digital said it would be working with Britain's National Cyber Security Center to resolve the outage.
The attack may have broader implications beyond England's health service.
"This attack was not specifically targeted at the NHS and is affecting organisations from across a range of sectors," NHS Digital said in its statement.
The organization said it did "not have any evidence that patient data has been accessed."
The statement identified the culprit as a type of malware known as Wanna Decryptor.
Internal tech systems were reportedly down in hospitals ranging from the center of London to rural parts of the country's south and north. Doctors were using pen and paper as the National Health Service struggled to get computers back online.
The attack reportedly affected emergency services in some locations, and patients were urged to avoid visits to the emergency room unless absolutely necessary.
Routine appointments were also being canceled.
The BBC reported that a list of affected locations included London, Blackburn, Nottingham, Cumbria and Hertfordshire.
Cybersecurity has been high on the agenda of many high-level gatherings of Western military and political leaders.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)