We recently wrote about how the growth of mobile messaging apps are challenging social networks and Line, one of the most prominent in Asia, has shown further evidence of that threat by passing 50 million downloads, and revealing that it is growing at a rate of 1 million new sign-ups per week.

The figure — which includes both iOS and Android downloads — comes just 13 months after the app was first released in June 2011, and NHN, the Korean Web giant behind the app, is aiming higher still.

As we’ve written before, the company expects Line to reach 100 million users by the end of 2012 with plans to increase its focus on China and North America by introducing new features and expanding support to other devices.

line 50m 520x424 Asian mobile messaging app Line passes 50m downloads, sees 1m new sign ups per week

NHN reveals that Line — which was developed by its Japanese subsidiary — has been ranked top of the free app category in the App Store across more than 24 countries. The firm has used the viral buzz of the store and Google Play to build a strong user base, which spans 230 countries.

Recently, Line made a move towards multimedia — increasing its rivalry with social networks — when it introduced Line Channel, a content hosting platform that allows users to share games, apps and other digital content through the service.

The move also saw the company open its API to developers, as it looks to grow the platform and go beyond providing the means to communicate via messages and voice calls.

The first apps, each of which is developed by Line, have shown some promise. Among them, Line Birzzle racked up 2 million downloads in its first 24 hours and has now reached 5 million downloads since its July 4 launch.

The company has other Line-themed apps — Line Camera and Line Card — both of which have seen millions downloads and are available connected to Line Channel or as standalone versions.

Line isn’t the only Asia-founded mobile messaging app making waves worldwide. Chinese Web giant Tencent recently added voice calling to its two competitors — Chinese app Weixin and global app WeChat — giving its 100 million plus registered users Skype like functionality.

The company is pushing WeChat heavily across Asia as it looks to gain traction within the region’s growing smartphone market.

Elsewhere, Korean app KakaoTalk has powered past 50 million users worldwide, having recently added VoIP-style free calling for its 30 million domestic users and 22 million overseas based users.

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Image via Flickr / Jenniferboyer