The highly anticipated iPhone 3G went on sale in the UK at 8:02am this morning.

However, many of those hoping to get their hands on the new phone may be disappointed as O2 has admitted to demand outstripping available stocks.

Apple is launching the iPhone 3G in 22 countries today, including Japan and New Zealand.

"We have never seen any mobile device create the excitement and demand of the iPhone 3G," said O2 UK chief executive Ronan Dunne.

O2 has said that limited stocks mean that many of its stores will have only a "few dozen" units for sale, which will be sold on a first come, first served basis.

Apple's new phone is also being sold at Carphone Warehouse and Apple stores around the country, but stocks are expected to be equally limited.

The flood of online pre-orders of the new device crashed O2's site earlier in the week.