has introduced its store for Google Android smartphone applications, further fuelling its wars with Apple., the online retailer also said yesterday the game Angry Birds Rio for Android is available for the first time exclusively through the Amazon AppStore.

The site is promoting the game, which is tied to News Corp’s Twentieth Century Fox animated film RIO featuring Angry Birds characters, by letting people download it for free for a limited time.

The move sets up Amazon as an alternative way to buy apps on tablet devices and smartphones, challenging Apple’s iTunes store.

And the AppStore comes just one day after Apple sued the company in a bid to stop the online retailer from allegedly improperly using Apple’s App Store trademark.

“What Amazon has… is consumer trust and credit card numbers,” said Sarah Rotman Epps, an analyst with Forrester Research. “By layering its payment system on the Android market, (Amazon) will grease the wheels for consumers to buy more Android apps.”

Consumers are able to use Amazon’s popular 1-Click payment option to purchase apps. Additionally, a feature lets people test an app on their computer before buying it.