Amazon's Australia launch was the company's biggest-ever opening day for orders, the US giant said Wednesday, but some shoppers were underwhelmed by the range of goods and prices on offer.

The country's retailers have been scrambling to lift their online presence and cut costs amid expectations that Amazon, one of the world's most valuable companies, would shake up the market and eat into their profits.

Amazon said first-day orders on Tuesday were "higher than for any other launch day" in its history, with "tens of thousands of customers visiting the website during the first 24 hours".