Apple has sold 525,000 iPhones since the product's US launch last Friday, Reuters reports.
The 6pm launch was marked by queues outside Apple and AT&T retail shops, with iPhone purchases limited to two per customer.
AT&T over the weekend reported that it sold almost all its initial stock of iPhones within hours of introducing the device.
"Virtually all of our stores sold out of the iPhone last night," AT&T spokesman Mark Siegel told Channel 4 News.
The LA Times cites analyst Trip Chowdhry of Global Equities Research, who claims half the Apple stores on the US West Coast sold out of the devices.
Analysts at Piper Jaffray also estimate first weekend sales of half a million handsets.
The device launched to an unprecedented wave of publicity, with wider technology industry news last week subsumed by reports looking at the Apple handset.
A new comScore study claims the hype has been matched by deep interest among US consumers.
It claims that an average of 274,000 iPhone-related searches have taken place each week since the announcement of the product in January.
Search activity peaked in recent weeks, reaching 1.2 million searches in the week ending June 24. This search activity has attracted 2.3 million visits to Apple's website, the report explains.
Approximately 2 per cent of early iPhone purchasers have been hit by problems activating their device, which they must do through iTunes.
AT&T has been working on the problem since it emerged. "We're just looking at everything to get customers activated in a timely fashion," said Siegel, who attributes the problem to the high number of customers trying to activate their phones.