LONDON — An extensive cyberattack hit Britain’s National Health Service on Friday, blocking doctors from gaining access to patient files, causing emergency rooms to divert patients and stoking fears about hackers’ ability to wreak havoc on vital public services.
Tom Donnelly, a spokesman for N.H.S. Digital, the arm of the health service that handles technology, said in a phone interview that 16 organizations, including “hospitals and other kinds of clinician services,” had been hit by a cyberattack.
“It is still ongoing,” he said. “We were made aware of it this afternoon.”
The service’s digital arm said in a statement that the attack involved a variant of ransomware known as Wanna Decryptor. Ransomware effectively takes a computer hostage and threatens to destroy data or continue to block access unless the victim pays a ransom.
On social media, several images circulated showing computer screens bearing a message that said the user could not enter without first paying a $300 ransom in Bitcoin.
N.H.S. Digital added, “At this stage we do not have any evidence that patient data has been accessed.”
It said that the N.H.S. did not appear to have been the target attack. There were reports on Friday of cyberattacks against companies in Spain and Portugal, but those accounts could not be immediately confirmed.
The National Cyber Security Center, an arm of the GCHQ, the British electronic surveillance agency, said it was investigating the attack. “We are aware of a cyber incident, and we are working with N.H.S. Digital and the National Crime Agency to investigate,” it said in a statement.