The areas will receive a further funding of AU$5.5 million over the next 18 months.
Over the last two years, Optus has built 12 mobile base stations in Riverina and Farrer -- with another eight in the pipeline.
In Indi, the company has installed 11 new sites since 2003 with an additional six installations by September 2006.
"Our mobile GSM network expansion is worth nearly AU$1 billion in NSW and Victoria.
"In the past two years we have increased our regional and rural mobile coverage by more than 200,000 square kilometres across Australia," said Paul Fletcher, Optus' Corporate and Regulatory Affairs director.
Fletcher said broadband services were also a priority for Optus.
"Australians living in regional areas can take advantage of Optus' satellite broadband at prices comparable to metropolitan customers via the government's Higher Bandwidth Incentive Scheme (HiBIS)," he said in a statement.
Meanwhile, Telstra has boosted its ADSL broadband offering with a AU$140,000 upgrade of the telephone network area in Wagga, New South Wales. The telco giant said AU$28 million had been earmarked for a nationwide upgrade of the service.
"As the region falls within the eligible area for the government's Higher Bandwidth Scheme, Telstra also intends to claim subsidies for the ultimate connection of those customers in the area that meet the general HiBIS criteria," said Andrew Cottrill, Telstra Country Wide Area general manager for Riverina Murray.
Since the commencement of HiBIS in last April, Telstra said it used the incentives to upgrade 260 rural and regional exchanges with ADSL services, and a further 260 exchanges were approved for upgrade this financial year.