In a statement provided to ZDNet Australia, Optus said that store stock for the iPhone 4 was "all but sold" after the first day of sales. Optus expects to receive another shipment of the smartphone from Apple in the next week, but is advising customers that it may be up to four weeks before they receive their iPhone 4, as the demand might outstrip the shipment size.
The company had received 100,000 pre-orders for the product prior to the launch.
Vodafone's Twitter account also indicated that the device had been a big seller, saying it had "limited stock".
Telstra had also experienced high demand for the phone.
"The iPhone 4 has been flying out the doors at Telstra stores across Australia... At many stores we have temporarily sold out of 32GB iPhone [handsets]; however, we're replenishing stock as quickly as possible and taking down our customers' details so they can purchase them as soon as new stock arrives."
Many customers have turned to the telco's Twitter account to ask whether stores still have any stock available; however, the company's social media representatives have said they are not aware of the stock levels of individual Telstra outlets.
Updated at 9:00am, 2 August 2010: included additional comment from Telstra.