The Galaxy S3 continues to sell at great speed, with Samsung announcing Thursday that 20 million devices have now been sold since it made its debut 100 days ago. The phone is the Korean tech company’s fastest-selling handset to date.

Samsung was confident from the start that the high-end S3 would do magical things for the electronics giant, with its head of mobile communications, JK Shin, claiming on launch day back in May that it would sell 10 million units before the end of July. It managed the feat with more than a week to spare.

This week it was reported that in August the S3 outsold Apple’s iPhone 4S for the first time since the 4S hit the market in October 2011 – though of course, this could be down to some Apple fans holding off buying a new iPhone until later this month, when the so-called iPhone 5 is widely expected to make its debut.

Sales of the S3 may be impressive, but if the expected iPhone 5 sells like the 4S did earlier this year – 35.1 million units in the first quarter – then it’ll soon slip back behind Apple as the smartphone of choice for the majority of users. Some analysts predict sales of the new iPhone could top 10 million within a week of going on sale.

Also, there’s a chance that sales of the S3 could drop to zero overnight – at least in the US – if Apple succeeds in its attempt to have the device banned from sale over the matter of patent infringement.

For the time being though, the Korean company will be more than happy with the way its Android-powered S3 is moving off the shelves. Consumers have been attracted by its sleek design, large 4.8-inch screen and array of features, including face-, gesture- and voice-recognition functionality. A powerful 8-megapixel camera which, among other things, allows you to take photos while recording video, has also helped it to stand out from the crowd. Now, how long before it notches up its 30 millionth sale?