Oliver Peterson: Australian correspondent on the aftermath of the region's nationwide Optus outage - Heather du Plessis-Allan Drive

The Australian Government's launching a review into the nationwide Optus outage affecting millions.

Customers started to report an inability to access both mobile and home internet services around 6am yesterday - with emergency services unable to communicate and trains in Melbourne brought to a halt.

Services are gradually being restored.

Australian correspondent Oliver Peterson says millions of Australians were left 'vulnerable' as a result of the outage.

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