Online retail giant Amazon has finally launched its Appstore for Android in the US, offering around 3,800 paid and free Android apps including Angry Birds Rio.

Amazon is trying to cash in on the rising popularity of smartphone apps and the rapid growth of Google's Android mobile phone OS. Amazon's Appstore will be competing with Google's own store for Android apps, the Android Market.

Users will be able to access the appstore via an Android app or from Amazon's website. Some of the apps on the Appstore will be priced less than their counterparts on the Android Market. Rovio will also be offering its new Angry Birds Rio game exclusively on Appstore for a limited time before launching it on Android Market.

The retailer, however, has launched the store only in the UK and has failed to mention when it plans to offer the store here in the UK.

“We are launching now in the US, however we are a global business and we will continue to evaluate opportunities to do what’s in the best interest of our customers. At this time, we have not announced plans on international launches,” an Amazon spokesperson told (http://www.metro.co.uk/tech/858757-amazons-appstore-for-android-gets-us-launch-but-no-uk-launch-date) Metro.

Amazon's platform has also caught Apple's attention, with the iPhone maker filing a trademark infringement lawsuit against Amazon to protect its 'App Store' trademark.