Microsoft is scrambling to fix an outage of some of its systems that has caused huge disruption to users, organisations and businesses across the globe.

The tech company said it was “seeing positive results” in its efforts to improve capacity to enable more users to get back on its systems, after a global outage affected millions of users for more than 12 hours on Thursday and Friday.

In an update shortly after 7am GMT, it said: “We’re seeing positive results for server stability after applying an upstream authentication/routing configuration component patch to a portion of our infrastructure.

“We’ll continue to monitor its progress and are working to expand it to servers supporting active regions coming online.”

The issue appears patchy, with some but not all users reporting problems with services including Microsoft Teams and Outlook email. More than 430 million people use Microsoft 365 apps, and more than 90% of Fortune 500 companies use Copilot, Microsoft’s AI chatbot, according to the company.

Microsoft said that there were no indications that the outage was caused by a cyber-attack.

Earlier, the company had said it was only seeing “marginal success” from its efforts to bring its systems fully back online. It had said that a portion of its infrastructure was “experiencing elevated load” – which was “likely contributing to the connectivity errors”.

The company determined a number of servers were “unexpectedly unavailable” because of a problem that caused them to fail during automated checks.

It earlier warned that services that have restarted can become unresponsive again once they receive traffic.

“Once mitigated, we will provide full details of the root cause, defence-in-depth repair items, and more within a post-incident report,” Microsoft said.

The outage website Down Detector showed an increase in Microsoft 365 problems at about 6pm GMT on Thursday, with nearly 130,000 reports of problems in 74 countries affecting access to Word, Excel, PowerPoint, Outlook and Teams as well as enterprise services such as SharePoint and OneDrive. AI assistant Copilot was also affected.

Microsoft has suggested the outage may have been caused by problems with the settings applied to servers responsible for keeping Microsoft 365 up and running.

Microsoft’s executive vice-president of Copilot, Charles Lamanna, posted on X that the company would share more information when it became available. “We regret that today’s outages caused disruptions for our customers, and we are working to address the issue,” he said.

The Microsoft outage also hit connectors used by ⁠OpenAI’s and Anthropic’s AI ⁠services.

OpenAI said it was investigating an issue with Microsoft connectors in which new connections may be broken and tools were not working as ⁠expected. Anthropic said it had identified an issue with an upstream provider ​affecting its Microsoft 365 ​connector.

The UK government said it was “working closely” with Microsoft to assess any impact on government services, adding that there were “robust contingency plans in place to minimise disruption”.

The outage has affected businesses and organisations across the world that use Microsoft products.

Several UK police forces have urged people not to try to report crimes online and to phone them in instead.

Some schools in the UK have notified parents that services such as email and Teams are down, and that reporting attendance or absence issues has to be done via phone. A primary school in Salisbury reassured parents that, while school communications have been disrupted, classes will not be affected.

An NHS provider to London, Milton Keynes and Surrey said email was disrupted and apologised for the inconvenience.

The Indian airlines IndiGo and Akasa Air said their email support services were affected, and Taiwanese security firms, life insurers and investment trust companies said fund management services had been disrupted.

In financial markets some portfolio managers have been unable to check emails, making it hard to access on some trading platforms.

In Japan, the shipping company Sagawa Express said it was unable to accept online reservations for some of its services at airports and train stations while Taisho, a major pharmaceutical company, said it was having to handle orders by phone.

In Australia experts estimate the outage will cost its economy billions of dollars.

Microsoft last month reported an ​outage of its Azure cloud platform that affected a ​suite of productivity software ‌and a range ​of industries worldwide.

Mark Gregory, an associate professor in the School of Engineering at RMIT University, said the outage appears to be affecting the network layer in Microsoft’s systems, and was potentially similar to the configuration issue that brought down Optus’s network in 2023.

He said when some of the servers have configuration issues, it means customers are forced to share a smaller pool of servers to access the cloud services.

“If you lose part of that pool, then all of the users are trying to access the remaining servers, and that overloads them. And then they go down.

“And so you end up with a cascading problem. Then it takes time to find the underlying problem, in this case, a misconfiguration in the network layer.”

Gregory said it showed companies should invest more in testing environments for configuration changes before deployment in the live network, and said businesses reliant on cloud services such as Microsoft 365 should have backup options.

“From a global perspective, there is someone somewhere that’s been badly affected by this and you end up with lost productivity,” he said.

“They’re being left high and dry now … it then becomes important to have an alternative.”

Earlier, the company said it had “successfully restored” problems related to Microsoft Teams in North America, although some users continued to report connectivity issues.

Associated Press and Reuters contributed to this report