The Industry Ministry says the attack affected the Windows operating system of employees' computers, blocking files and demanding a ransom to free up the system.
Hospitals across England reported the cyber attack was causing huge problems to their services and the public in areas affected were being advised to only seek medical care for emergencies.
At the Royal London Hospital operations were cancelled and staff were ordered not to touch their computers.
Blackpool Hospitals NHS Trust in northwest England, which includes six hospitals, said: "Please don't attend A&E (accident and emergency) unless it's an emergency".
"Unlike most other attacks, this malware is spreading primarily by direct infection from machine to machine on local networks, rather than purely by email", Lance Cottrell, chief scientist at the U.S. technology group Ntrepid.
NHS Digital recently confirmed that the recent NHS cyberattack used the Wanna Decryptor ransomware to infect the systems of at least 16 United Kingdom trusts.
The attack on the National Health Service seemed perhaps the most audacious of the attacks, because it had life-or-death implications for hospitals and ambulance services.
The National Cyber Security Center said it is "aware of a cyberincident".
It said its hospitals had shut down all computer systems as a protective measure and canceled all non-urgent activity.
In Italy, one user shared images appearing to show a university computer lab with machines locked by the same program.
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.
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The most high-profile attack surfaced early Friday when Britain's National Health Service (NHS) reported that at least 16 of its hospitals had received ransomware, which takes control of a person's computer.
"It is going to spread far and wide within the internal systems of organizations - this is turning into the biggest cybersecurity incident I've ever seen", UK-based security architect Kevin Beaumont said.
Shortly after that disclosure, Microsoft announced that it had already issued software "patches" for those holes.
Security researchers are reporting a massive attack today, dubbed "WannaCry", which has reached 45,000 attacks in 74 countries around the world so far, mostly in Russian Federation.
Researchers spent much of Friday examining the software used in the attack, and believe it relies on re-purposed code that is said to have originally been written by the NSA.
A spokeswoman for Portugal Telecom said: "We were the target of an attack, like what is happening in all of Europe, a large scale-attack, but none of our services was affected".
Among the companies targeted was USA -based FedEx. "No computers are now working", they said, speaking on condition of anonymity as they were not authorised to speak to press. But there's no evidence so far that patient data has been accessed, NHS Digital said.
Stephen Hirst, a doctor in the northern English town of Preston, told the BBC that the first sign of the infiltration was an error message warning that "we'd have to pay money to unlock the computer because it's been encrypted".
It said the attacks had not affected the companies' services or data protection of their clients.
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