Telstra Group (ASX:TLS) said Wednesday it is investigating an outage that is impacting some mobile calls and data connections.

"Fixed internet services like NBN are not affected," the company told MT Newswires following multiple reports of the outage.

The issue has impacted hundreds of traffic lights in South Australia and has resulted in the suspension of regional train services in Victoria and New South Wales, ABC reported.

The issue appears to be widespread, with at least 6,000 people reporting an outage on Downdetector as of early Wednesday morning, according to the Australian Financial Review.

"We're on it and will share an update as soon as it's fixed," a Telstra spokesperson said.