But no details on promised speeds.

Optus claims to be "already upgrading" its hybrid fibre-coaxial cable network in three capital cities to DOCSIS 3.0 technology, but has declined to reveal to what speeds.

A spokesman released a brief statement yesterday, claiming that the upgrades were taking place on its HFC network in Sydney, Melbourne and Brisbane.

The statement was released within a few hours of Telstra announcing it had completed the DOCSIS 3.0 upgrade of its cable network in Melbourne.

"Further details will be announced shortly," the Optus spokesman said.

Optus was today unable to commit to a timeline on when the company would provide this detail. Nor could it confirm what the speed upgrade in the three cities would be.

Telstra announced yesterday it had completed an upgrade of its HFC cable network in Melbourne to the DOCSIS 3.0 specification, to allow download speeds of 100 Mbps and uploads of 2 Mbps.

A Telstra spokesperson also confirmed to PC Authority plans "to implement 30Mbits/s download speeds on the larger national HFC cable network...where services are currently running at 17Mbit/s".

Optus last formally announced an upgrade of its HFC network in December 2007, boasting average speeds of between 14 Mbit/s and 16Mbit/s.

The network is accessible by "1.4 million serviceable homes and businesses," the Optus spokesman said.

The spokesman said Optus was "constantly upgrading" its network.