Microsoft has apologised to customers in more than 70 countries after a technical fault knocked out its services from Thursday into Friday, insisting the disruption was not the result of a cyber-attack.

The US company expressed its "deep regret" over the outage, which hit Outlook, Teams and its Copilot AI tool. More than 430 million people worldwide use the affected products. Microsoft said the problem was technical, caused by a "network capacity upgrade", and had nothing to do with cyber-attacks or artificial intelligence systems.

By Friday afternoon, roughly 24 hours after the problems began, services were broadly recovering. The company reported "encouraging progress" and said email flow was returning to normal levels, adding that it was restoring services gradually because of "high demand".

Users first reported difficulty accessing Microsoft 365 products on Thursday. By Friday, the impact had spread to organisations ranging from the Japanese government, the Philippine Supreme Court and Australia's intelligence agency to rail services, hospitals and courts in North America.

In the UK, the outage disrupted the work of National Health Service staff, though the minister responsible for cyber security said the NHS 999 emergency and 111 helpline services were unaffected and there had been no disruption to transport. In Canada, hospitals and rail passengers were affected, while courts and government offices were hit in the United States. Operations in both countries are gradually returning to normal.

Technology experts described the incident as a "stark reminder" of how heavily businesses and critical services depend on a small number of tech giants. One cyber security consultant warned the global impact would be "absolutely huge".