LONDON — A number of hospitals and healthcare services across England were hit by an apparent cyberattack Friday, health care authorities said.

The National Health Service in England confirmed the hacking. Services in London, the central city of Nottingham, and the counties of Hertfordshire — north of London — and Cumbria — in northern England — were affected, according to the BBC.

The hackers behind the "ransomware" attack were demanding $300 in electronic currency to release files from encryption, the Mirror reported.

East and North Hertfordshire NHS trust, which runs four hospitals north of London, said in a statement: "Today, the trust has experienced a major IT problem, believed to be caused by a cyberattack.

“Immediately on discovery of the problem, the trust acted to protect its IT systems by shutting them down; it also meant that the trust’s telephone system is not able to accept incoming calls.”

It said it was postponing all non-urgent work and asked people not to come to the accident and emergency unit.