Optus has confirmed that voice services have been restored across its mobile network following intermittent disruptions on Friday morning.

According to the telco, the brief outage was caused by a “technical hardware failure”.

“Mobile data services were fully operational and were not affected,” an Optus spokesperson said.

“Optus can confirm services were restored at 9.20am AEST and apologise to customers who experienced any inconvenience and thank them for their patience.”

Optus in May reported having 10.106 million mobile customers — 3.7 million in prepaid, 5.3 million in post-paid, and 1.1 million in mobile broadband — as of the end of March, bringing in AU$5.2 billion in consumer mobile revenue during FY17.

Optus built 366 new mobile sites during the financial year, and upgraded 6,783 mobile sites to 4G. Almost 5,800 of these sites were upgraded to 700MHz spectrum, with its 4G network now reaching 96.9 percent of the Australian population.

Vodafone Australia similarly suffered a voice outage in March across its mobile services, attributing the issue to a fault during scheduled work.

This came after Vodafone’s voice outage lasting around three hours back in January, which was caused by an error during planned work on the network.

Rival carrier Telstra has also been subject to a number of outages this year, including wholesale mobile virtual network operator (MVNO) customers being impacted across 3G and 4G services as a result of a “vendor platform issue” in June; a fibre cable cut earlier that month, which…