Pyotr Lidov, a spokesman for Megafon, said Friday's attacks froze computers in company's offices across Russian Federation.
His move may have saved governments and companies millions of dollars and slowed the outbreak before US -based computers were more widely infected.
The Spanish government said several companies including Telefonica had been targeted in ransomware cyberattack that affected the Windows operating system of employees' computers.
German rail operator Deutsche Bahn said some electronic signs at stations announcing arrivals and departures were infected.
Microsoft President Brad Smith, in a blog post Sunday, said the attack is a "wake-up call" for governments in the USA and elsewhere to stop stockpiling tools to exploit digital vulnerabilities.
"This attack was so simple and unsophisticated, that leads me to believe the people or person involved, even though they are quite capable, they're more along the lines of an amateur", he said. Xinhua state news agency said some secondary schools and universities were hit.
Images appeared on victims' screens demanding payment of $300 (275 euros) in Bitcoin, saying: "Ooops, your files have been encrypted!"
Researchers are racing against the clock to try to decrypt infected computers and recover access to victims' files before the malicious code's ransom deadline expires in two days. It was reported that a hacking tool known as "Eternal Blue" was created by NSA to break into the computer systems of terrorist organizations.
"All of our hospitals remain open for emergency care, though some ambulances continue to be diverted to neighbouring hospitals", Barts Health NHS Trust said in a statement.
"We are aware of widespread speculation about the use of Microsoft Windows XP by NHS organisations, who commission IT systems locally depending on population need".
Computer users worldwide - and everyone else who depends on them - should assume that the next big "ransomware" attack has already been launched, and just hasn't manifested itself yet, Eisen said.
Barts Health NHS Trust, the largest NHS trust in the country, has said it was continuing to experience IT disruption, leading to delays and cancellations for patients.
Cyber security experts say the spread of the virus dubbed WannaCry - "ransomware" which locked up computers in auto factories, hospitals, shops and schools in several countries - has slowed, but that any respite might be brief.
A Nissan Motor Co. plant in northeast England also was affected without causing any major impact on business, an official said.
RSN chief executive Graham Biggs said: "This is an extremely worrying situation for rural patients and for small rural practices which operate on a limited budget".
Other Spanish firms to be hit included power firm Iberdrola and utility provider Gas Natural.
Technical staff scrambled on Sunday to patch computers and restore infected ones, amid fears that the ransomware worm that stopped auto factories, hospitals, shops and schools could wreak fresh havoc on Monday when employees log back on.
In the United States, package delivery group FedEx said it was "implementing remediation steps as quickly as possible", while French carmaker Renault was forced to stop production at sites in France, Slovenia and Romania.
On Monday the firm said that 90% of its factories were running again. News.com.au reported the minister told reporters in Cairns that the challenge was that there were various instances of ransomware in Australia every week and authorities were now seeking to confirm whether these are the same thing that hit the United Kingdom.
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