Japanese eCommerce firm Rakuten has acquired OTT service Viber for $900m (£539m).

Viber offers free messaging and VOIP calls through its apps, which total 300m registered users. Its a crossplatform service, spanning all four of the major smartphone platforms and feature phone OSs Symbian and Bada, as well as desktop. It started to monetise its service with the launch of paid stickers last September.

Rakuten, which owns Play.com in the UK and host of other eCommerce site across the global, has previously made steps into the digital content space with its acquisitions of eBook and eReader company Kobo and Wuaki.tv and Viki, two VOD streaming services operating in Europe and Asia respectively.

Its not clear at this point exactly how Rakuten will be incorporating this acquistion into its operations. The official statement says the company will leverage [Viber] to expand business opportunities and to grow its global membership, and suggests its part of a strategy to build a digital content business to match its eCommerce and financial service arms. Weve reached out to a Rakuten spokesperson for more details, and to find out if Viber will continue to operate as an independent app.

“Simply put, Viber understands how people actually want to engage and have built the only service that truly delivers on all fronts,” said Rakuten chairman and CEO, Hiroshi Mikitani. “This makes Viber the ideal total consumer engagement platform for Rakuten as we seek to bring our deep understanding of the consumer to vast new audiences through our dynamic ecosystem of internet services.”