Microsoft says the major network outage caused by a security software update affected an estimated 8.5 million Windows devices.

The disruption, which occurred on Friday, affected airlines in Europe, Asia and the United States. Hospitals in the Middle East and a broadcaster in Britain were hit as well.

Microsoft says it happened when US cybersecurity firm CrowdStrike released an update of its Falcon content for Windows.

Microsoft said on Saturday that less than one percent of all Windows machines were affected.

But it said "while the percentage was small, the broad economic and societal impacts reflect the use of CrowdStrike by enterprises that run many critical services."

The outage is still causing some confusion but it is mostly contained.