The latest sales figures from research firm NPD Group show Apple's iPhone 3G gaining market share rapidly.

The handset now accounts for 17 per cent of the market, second only to Motorola's RazR2. Before the iPhone 3G launch Apple's market share was 11 per cent.

The survey of over 150,000 consumers also found that 30 per cent of iPhone buyers switched networks to AT&T to get the phone.

Verizon Wireless was the biggest loser, at 47 per cent of that figure, followed by 24 per cent from T-Mobile and 19 per cent from Sprint.

"The launch of the lower-priced iPhone 3G was a boon to overall consumer smartphone sales," said Ross Rubin, NPD Group director of industry analysis, in a statement.

"While the original iPhone also helped win customers for AT&T, the faster network speeds of the iPhone 3G proved more appealing to customers who already had access to a 3G network."

Rubin noted that the iPhone is now outselling the BlackBerry Curve, BlackBerry Pearl and Palm Centro, making it the number one smartphone in the US.