It seems like there is no stopping Asian messaging app Line right now, and the service — developed by NHN Japan — has now topped 60 million registered users, according to an announcement made today.

Line’s rise exemplifies the addressable market for smartphones and apps in Asia, and download numbers for the app — which allows users to send text messages and place voice apps for free using an Internet connection — have doubled since April, just 5 months ago.

NHN Japan says that, since passing 50 million downloads in July, its growth has reached 5 million new sign-ups every three weeks, that’s even quicker than the 1 million per week it was seeing in July.

pressline6000 520x467 Line passes 60m downloads, sets its sights on the US, China and reaching 100m

So, what now? Global dominance…well almost. NHN has two ambitious targets: reaching 100 million downloads before the end of the year and cracking new markets, specifically China and the US.

With 15 weeks left until 2013, growth is going to need to continue to accelerate if the company is to crack 100 million, while it will face a stiff test to launch in these two vast markets. Expanding its international footprint is hugely key to its growth target.

Tencent is dominating the Chinese messaging app scene, with more 100 million users, and, what’s more, its WeChat service is making inroads in Southeast Asia, a market where Line is already well-placed. The fact that Line has competed so strongly against globally popular WhatsApp, and fellow Asian service KakaoTalk, shows that most consumers are open to using more than one app – however localizing in China and beating the copycats are challenges that are almost entirely new to the company.

The US itself is a tough market to enter. Not only are rival products such as Viber or Microsoft-owned Skype already popular, but Line will need to buck a very serious trend for Asian startups. To date, companies from the continent have found it difficult launching Stateside, and there’s no role model for success yet.

Either way, the Line business is operating well within Asia and its Sticker Shop — which sells virtual stickers/cartoon images that users can send to each other — racked in more than $3.8 million (300 million yen) in profit during August alone.

It remains to be seen how well stickers would do in the US, where attitudes to virtual goods are much different to Asia, but — with more users than Instragram pre-acquisition – Line is already a global phenomenon, regardless of whether it becomes mainstream in the West.

Headline image via Flickr / TaxFix.co.uk