Optus has confirmed that its mobile network is experiencing an outage across Australia.
"Some Optus customers this morning may have been experiencing intermittent disruptions to their mobile services," an Optus spokesperson said on Friday.
"We have been progressively restoring services since 10am.
"We apologise to our customers for any inconvenience experienced and appreciate their patience while services were being restored."
Friday's service disruption follows Optus similarly experiencing a loss of voice services on its mobile network last month, which it said had been caused by a "technical hardware failure".
"Mobile data services were fully operational and were not affected," an Optus spokesperson said in August.
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 affected wholesale mobile and fixed-line services and several thousand broadband and ADSL services; a mobile outage that was caused by a software fault, which it said "triggered multiple elements across the network to fail", in May; Telstra dropping Triple Zero call services as a result of fibre damage near Orange, New South Wales, also in May; and a 4G voice network outage following "technical changes made ahead of upgrades to mobile traffic control equipment in Telstra's Exhibition Street exchange in Melbourne".