Radically increasing the screen size of Apple's iPhone 6 range has paid off as pre-order sales reached a record 4 million in the first 24 hours.

Chief executive Tim Cook said "pre-orders for iPhone 6 and iPhone 6 Plus set a new record for Apple."

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Sales of the iPhone 6 and 6 Plus doubled that of the previous iPhone to be offered for pre-order, the iPhone 5, which sold 2 million units during its first 24 hours in 2012.

"Demand for the new iPhones exceeds the initial pre-order supply", it said in Apple's statement. "While a significant amount will be delivered to customers beginning on Friday and throughout September, many iPhone pre-orders are scheduled to be delivered in October."

Presales opened at 5pm on Friday to such demand it caused the websites of Apple, Optus, Telstra and Vodafone to crash.

Research firm Telsyte forecasts 1.5 million new iPhones will be sold by the end of the year in Australia, or 100,000 iPhones per week on average over the peak holiday season, provided Apple can keep up with the demand.

Telcos are already quoting a wait time of one month on select models and are hoarding the larger iPhone 6 Plus due to limited stock supply. Telstra and Virgin list the larger Apple iPhone 6 Plus as out of stock on their websites, while Vodafone and Optus are not sparing stock of the smartphone for pre-orders.

"We had 30,000 calls per minute to our eStore," a Vodafone spokesperson told Good Gear Guide.

The most popular model so far for Vodafone is the 64GB variant of Apple's iPhone 6 in space grey.

Apple's iPhone 6 range goes on sale in stores on 19 September from Vodafone, Optus, Telstra, Virgin and Apple stores.