Dozens of countries, including US, hit by huge cyberextortion attack

"We're not aware of any evidence that patient data has been compromised".

The IT systems of these hospitals went down simultaneously.

Around 40 NHS trusts and several GP practices in England and Scotland - but not Wales or Northern Ireland - have also been hit with the ransomware. Routine appointments had been cancelled and ambulances were being diverted to neighbouring hospitals.

These boards are NHS Borders, NHS Dumfries and Galloway, NHS Fife, NHS Forth Valley, NHS Lanarkshire, NHS Greater Glasgow and Clyde, NHS Tayside, NHS Western Isles, NHS Highlands, NHS Grampian, NHS Ayrshire and Arran and Scottish Ambulance Service.

Cybersecurity firm Avast said it has tracked more than 75,000 attacks in 99 countries. By the time she finished speaking, similar attacks had been reported on business targets across Europe including Spain's telephone system.

With the cyber attack, the software of NHS was blocked and doctors were blocked from patient files.

Dr Krishna Chinthapalli, a neurology registrar at the National Hospital for Neurology and Neurosurgery in London, had warned that an increasing number of hospitals could be shut down by ransomeware attacks in an article on the vulnerability of the NHS network in the "British Medical Journal" on Wednesday, two days before the major cyber-hack.

The British government did not know who was behind the attack but its National Crime Agency was working to find out, interior minister Amber Rudd said.

Pictures on social media showed screens of NHS computers with images demanding payment of $300 (230 pounds, 275 euros) in Bitcoin, saying: "Ooops, your files have been encrypted!"

WannaCry is a form of "ransomware" that locks up the files on your computer and encrypts them in a way that you can not access them anymore. As per the reports, few payments has been made around the world.

Alan Woodward, visiting professor of computing at the University of Surrey, said there was evidence the ransomware was spreading using a Microsoft flaw exposed in a recent leak of information from U.S. intelligence agencies. Microsoft released a patch (a software update that fixes the problem) for the flaw in March, but computers that have not installed the security update remain vulnerable.

NHS Digital said the attack, believed to have been caused by a malware variant, did not specifically target the NHS and it is also affecting various sectors.

NHS Digital said it was working with the government's National Cyber Security Centre, the Department of Health and NHS England to help the organizations affected "manage the incident swiftly and decisively". An Interior Ministry statement says 85% of Telefonica computers have been affected.

Germany's Deutsche Bahn computers were also impacted, with the rail operator reporting that station display panels were affected. In seven days, the attackers say all encrypted files will be wiped out.

The ransomware, called Wana Decryptor or WannaCry, has been found infecting machines across the globe.

Britain's National Cyber Security Centre and its National Crime Agency were looking into the United Kingdom incidents, which disrupted care at National Health Service facilities.

A massive cyberattack hit dozens of countries Friday, paralyzing Britain's national heath service.

Friday's unprecedented ransomware attack may have stopped spreading to new machines - at least briefly - thanks to a "kill switch" that a security researcher has activated.