The ransomware appeared to exploit a vulnerability in Microsoft Windows that was purportedly identified by the U.S. National Security Agency for its own intelligence-gathering purposes.
The ransomware attack hit a range of organisations in at least 99 countries.
Security software company Avast reported "more than 57,000 detections".
"For those organizations who have not yet applied the security update, we suggest you immediately deploy Microsoft Security Bulletin MS17-010". Europol called the attack "unprecedented", and that its cyber-crime division was working to "mitigate the threat and assist victims" in affected countries.
"Like many organisations our plant was subject to a ransomware attack affecting some of our systems on Friday evening", said a spokesman.
Health Secretary Shona Robison said there was no evidence that patient data had been compromised.
While no German government agencies were believed to have been affected, Russia's Interior Ministry said about 1,000 of its computers were hit.
Home Secretary Amber Rudd is to chair an emergency meeting as tech experts work to disrupt an worldwide cyber attack which has crippled NHS services across the country.
Krishna Chinthapalli, a doctor at Britain's National Hospital for Neurology & Neurosurgery who wrote a paper on cybersecurity for the British Medical Journal, warned that British hospitals' old operating systems and store of confidential patient information made them an ideal target for blackmailers.
"Both staff and patients were frankly pretty appalled that somebody, whoever they are, for commercial gain or otherwise, would attack a healthcare organisation", he said.
Telecommunications giant Telefonica was among the targets in Spain, though it said the attack was limited to some computers on an internal network and had not affected clients or services.
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It has affected 45 NHS organisations, Ms Rudd said.
A cyber strike which hit dozens of British hospitals today is part of a wider "international attack", Prime Minister Theresa May said.
"The investigation is at an early stage but we believe the malware variant is Wanna Decryptor", NHS said.
It is understood that several health trusts turned their computer systems off as a precautionary measure, rather than being shut down by the attack.
Labour leader Jeremy Corbyn branded the attackers a bunch of 21st Century highway robbers and said the Government should have renewed a multimillion-pound security package.
She added: "Where the patient data has been properly backed up, which has been in most cases, work can continue as normal because the patient data can be downloaded and people can continue with their work".
Governments and private security firms on Saturday that they expect hackers to tweak the malicious code used in Friday's attack, restoring the ability to self-replicate.
The security holes it exploits were disclosed weeks ago by TheShadowBrokers, a mysterious group that published what it said are hacking tools used by the NSA.
According to her, the number of health service trusts in England hit by yesterday's attack were 48 of 248, which is around one in five.
"The National Cyber Security Centre is working closely with NHS Digital to ensure they support the organisations concerned and that they protect patient safety".
The Barts Health group, which manages major central London hospitals, including The Royal London and St Bartholomew's, said it had activated a major incident plan and had cancelled routine appointments.
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