There's a global cyberattack happening that's taking down hospitals and telecoms companies

In the United Kingdom, sixteen organizations in the National Health Service were infected, and hospitals in London, North West England and Central England urged people with non-emergency conditions to stay away as technicians tried to stop the spread of the malicious software.

"At this stage we do not have any evidence that patient data has been accessed", the system says.

"Hospitals across England have been hit by a cyberattack", leaving patient files inaccessible, according to the National Health Service (NHS). The hospital was only allowing patients requiring immediate and emergency care to be admitted. Other affected locations included NHS Glasgow, Dumfries and Galloway, Forth Valley and the Western Isles.

A police spokesperson said they're not aware of any incidents in New Zealand related to the attacks but have informed Ministry of Health officials as a precaution. "This is not targeted at the NHS". Experts warned that online extortion attempts by hackers are becoming a growing menace.

Patrick Ward, a 47-year-old sales director, said his heart operation, which was scheduled for Friday, was cancelled at St. Bartholomew's Hospital in London.

"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.

He said many NHS hospitals in Britain use Windows XP software, introduced in 2001, and as government funding for the health service has been squeezed, "IT budgets are often one of the first ones to be reduced". In this case, the attackers leveraged the vulnerability to infect systems and demand a ransom of between $300- $600 in order to secure their release. If you have been following Microsoft's Patch Tuesday schedule, then your machines should already be protected. They even attached a clock with the time left to make the payment.

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 US intelligence agencies.

Leading worldwide shipper FedEx Corp was among the companies whose Microsoft Corp Windows systems were affected.

Tom Griffiths, who was at the hospital for chemotherapy, said several cancer patients had to be sent home because their records or bloodwork couldn't be accessed.

Meanwhile, Kaspersky Lab, a cybersecurity company based in Moscow, has published a blog post in which it estimates that 45,000 attacks have been carried out in 74 countries, mostly in Russian Federation.

At least 16 organisations within the NHS, some of them responsible for several hospitals each, reported being targeted.

Spain, meanwhile, said several Spanish companies had been targeted in ransomware cyberattack that affected the Windows operating system of employees' computers. Authorities said they were communicating with more than 100 energy, transportation, telecommunications and financial services providers about the attack.

Images that were posted online of the NHS pop-up look almost identical to pop-up ransomware windows that hit Spain's Telefonica, a powerful attack that forced the large telecom to order employees to disconnect their computers from its network and to resort to an intercom system to relay messages, according to Bleeping Computer.

The attacks are being caused by ransomware called "WannaCry", which quickly moves across systems to encrypt large amounts of computer data.

British government officials and intelligence chiefs have repeatedly highlighted the threat to critical infrastructure and the economy from cyberattacks.

"Once it gets in and starts moving across the infrastructure, there is no way to stop it", said Adam Meyers, a researcher with cyber security firm CrowdStrike.

Ransomware attacks are the latest trend in cyber attacks around the world.