Up to 700,000 Apple iPhones were sold in the launch weekend, according to the latest Goldman Sachs analyst research. This has prompted concerns that the higher than expected demand could lead to iPhone shortages.

The estimates are even higher than the initial figures quoted yesterday by Piper Jaffray and Global Equities Research. They estimated weekend iPhone sales at around 500,000 and 525,000, respectively.

The higher than expected iPhone sales estimates come amid reports that iPhone availability in Apple Stores is being squeezed by the huge demand.

According to Engadget , the online Apple Store retail availability indicator showed that availability dropped on Monday from 84 per cent to 61 per cent. This morning it showed 42 per cent availability across US stores, although some stores which were out of stock after the weekend have now been restocked.

AT&T stores, however, are still waiting for new stocks of the iPhone after selling out quickly over the weekend, according to reports from the US. Would-be Apple iPhone buyers can order the iPhone online, although there is a 2-4 week delivery time for online orders.

Stocks of 8GB iPhones are believed to be in shortest supply. Analysts are estimating that demand for the higher capacity iPhone has been stronger than for the 4GB version.